Also, this isn't a canon thread. I'm only talking about the BoG/FnF movies & Super manga. And no, it isn't the 2 base theory either. BTW, the anime is its own continuity with its own rules, so I won't take it into account (without saying that it's non-canon or bad, I love it).
Toriyama wrote the scripts for the movies DBZ: Battle of Gods & DBZ: Ressurection "F", as well as story outlines for the Universe 6, Future Trunks, and Universe Survival arcs of Dragon Ball Super, and all of them together create a big story that is supposed to happen in the same continuity as the original manga. Toei adapted these stories into an anime series, and Toyotaro adapted them into a manga series, but while the anime is a complete adaptation of these stories, the manga isn't. The Battle of Gods arc is heavily reduced, and the Ressurection "F" arc is entirely skipped and any relevant information from it gets reffered by the narrator whenever it's necessary. So, we have the movie continuity which lacks the U6/FT/US arcs, and we have the Super manga continuity which lacks a huge part of BoG & 99% of FnF. So, why not combine the 2 movies & the 3 new story arcs together into 1 continuity? The only problem is, while the BoG arc of the manga has many differences & omissions, none of them are important... except for one: Goku absorbing the power of Super Saiyan God. In the manga, it never happened, and the story kept going with this fact. Both Goku & Vegeta appear to be at their regular levels in their base forms, they transform into their SS/2/3 forms, and Goku turns into SSG, which brings him far above SS3. This makes every version FnF (script, movie, promotional manga, even Super anime) impossible to happen, since in every version we have base Goku with SSG powers fighting Freeza. So, how can the movies & manga fit together? You could choose the simple answer and say "they fit, except the manga retcons things so that Goku never absorbs the SSG power & fights Beerus in base/SS, and Goku never fights Freeza in base". There is a problem however in this: Goku Black. And to explain that, I'll have to explain how the 3 god forms work in general, and how the movies & Super manga can fit together without retcons.
Goku became a Super Saiyan God by borrowing the light of 5 other righteous Saiyans, and it was supposed to last for a few minutes only. However, through his fight with Beerus, Goku absorbed the form's power in his base form, making him almost as strong as SSG in base, and making his regular Super Saiyan & Super Saiyan God forms useless (presumably along with Super Saiyan 2 & Super Saiyan 3). According to Beerus, Goku absorbed the power of SSG & his power didn't decrease significantly after the form disappeared, and after the form disappeared he went back to base, so that's where the power went. Goku didn't notice that he went from Super Saiyan God, to base, to Super Saiyan. He also fought in his base as good as he did in his SSG form, and he fought better in his SS form because he got angry. He also managed to destroy Beerus' Ball as a SSG, while he couldn't in base & SS, because he was angry there as well. Toriyama confirmed that SSG was useless at this point.
And while Goku can turn into a SSG now by himself, even though it's useless at this point, he doesn't know how to do it at will yet.Will Goku be able to transform into [Super Saiyan] God in the future?
I think you’ll understand if you watch [the movie], but Goku has already absorbed [Super Saiyan] God’s power and made it his own, so there is no need for him to transform into [Super Saiyan] God. Goku basically only thinks of fighting as a sporting match, so borrowing the power of five people isn’t fair, and he resisted doing that; however, it seems his curiosity towards the realm that lay even further beyond him won out.
About after BoG, and before FnF was even announced (but it was close to its announcement), Toriyama said this:
What could Toriyama mean by that? Why would Goku master his base & SS forms, which are already supposed to be mastered? And especially now that SS is useless?Goku endlessly keeps getting stronger, with Super Saiyan 3 in the manga and Super Saiyan 4 in the anime; does Super Saiyan keep getting limitlessly stronger too? Might we eventually see things such as a Super Saiyan 5…?!
Super Saiyan 2 and 3 are nothing more than powered-up variations of Super Saiyan. After the fight with Beerus, Goku realized that mastering his normal state and Super Saiyan would raise his level more and sap less strength, so I think he probably won’t become Super Saiyan 2 or 3 any more.
By the time FnF happens, Goku has trained under Whis. His base form is still super-powerful thanks to the SSG power, but his SS form is different now; it's blue, and it's stronger than SSG. Goku explained that this is his Super Saiyan form, but not exactly it, as it's the Super Saiyan form of a Saiyan who has the power of Super Saiyan God. Vegeta also calls it the legendary Super Saiyan form, as if it's the golden one. So, why didn't SS Goku turn blue against Beerus if he already had the power of SSG? What I believe is that after Goku mastered his SS form with the power of SSG, it evolved into Super Saiyan Blue, and the golden Super Saiyan form was gone (for now at least).
Vegeta also apparently went through the same proccess as Goku did; he became a Super Saiyan God, absorbed its power, and achieved Super Saiyan Blue. According to Toriyama, Goku trained with Whis first and then Vegeta followed, Vegeta didn't train first to catch up like in the anime:
But what about mastering the base form? In the U6 arc of the Super manga, it appears that Goku & Vegeta still have the power of SSG in their base, and they can't use their old golden forms. They spar in their base forms, and Vegeta turns into a SSB to overpower base Goku, and base Goku survives a ki blast (that was obviously supressed, but still) from SSB Vegeta. Why didn't Vegeta just turn into a regular Super Saiyan? Because I believe he couldn't. But after training inside the Room of Spirit and Time, they could use their golden SS/2/3 forms just fine, and SSG was very useful instead of useless. What changed? I believe they mastered the SSG power in their base forms & learned how to turn SSG at will, which resulted to their SSG power disappear from their base forms.Akira Toriyama’s Inside Story: Tell us the details on how they started training with Whis!
Goku was the one who asked Whis, of course. It was on condition that he give Whis tasty food! Vegeta didn’t want Goku to leave him in the dust, so he had no choice but to come train too.
And how does Goku Black/Zamasu fit in all this? Before Zamasu stole Goku's body, Goku had trained for years beyond his limits, and the near-death power-ups had stopped ever since Freeza arc. So, after Zamasu stole Goku's body & became Goku Blac, even though he shouldn't be able to use it at its fullest since he wasn't used to it yet, as his spirit & body weren't in balance yet, he shouldn't be able to get near-death power-ups anymore. However, not only he did, but his base form went up to beyond SS3 Goku's level, and then his regular SS form reached SSB Goku's & Vegeta's level through even more near-death power-ups. And after a last near-death power-up, his Super Saiyan form evolved into Super Saiyan Rosé. He didn't transform beyond SS, his SS form itself changed, and the change happened because SS Black surpassed Super Saiyan God according to Future Zamasu. Super Saiyan Rosé is his version of Super Saiyan Blue, but it's pink because Black has the power of a god as a Kaioshin. But why didn't Goku himself become a Super Saiyan Blue like this?
Here is what I believed that happened. The fact that Zamasu, a god, was in Goku's body was what allowed him to evolve further than Goku ever could. Why? I believe that this allowed Goku's body to tap into his SSG dormant powers through training & near-death power-ups. Because Black was a god, the SSG power was unlocked. But not all of it like when Goku absorbed it back in BoG, he didn't have any of it at the beginning. He slowly drew out more & more of it through near-death power-ups, which is why he was so unnaturally strong. And after he drew all of that power and surpassed SSG in his SS form, like Goku did after absorbing the power of SSG & training in his SS form, his SS changed into SSR, like Goku's SS changed into SSB.
This theory about Black is impossible if we just assume that the manga retconned the movies, so the theory about the SSG power going away from Goku's & Vegeta's base forms is necessary for this. But without this, Black doesn't make much sense, nor does Future Zamasu's explanation that Black became SSR because he surpassed SSG. And the theory about the SSG power going away makes a lot of sense, and it's even hinted to be the case in the manga since before the RoSaT, Goku & Vegeta appear to be super-powerful in their base forms & only appear to be able to turn SSB. This would also explain why SS Black has sparks, while everyone else doesn't; he was tapping to SSG's special power.
Any thoughts?