
Goku is treading deep on the path of the gods and angels. The last few story arcs have culminated in his ability to use Ultra Instinct at will, with Whis instructing him to use Ultra Instinct all the time, even while in base form (though the silver-haired 'Perfected' transformation is apparently still going to be kept around as a last-minute power boost until he can truly master it as a permanent state of being). His need for the golden Super Saiyan forms, including the coloured Super Saiyan God forms, is starting to wane. Unlike Gohan, Goku hones himself constantly, but with the path he's taking being antithetical to the emotion-fuelled Super Saiyan transformations of the past, could he possibly forget how to go Super Saiyan altogether?
Whis is drilling into Goku's primate brain that transformations are not the be-all-end-all for attaining greater strength. As the power of Ultra Instinct is orders of magnitude stronger than any Super Saiyan form could ever hope to be, could we theoretically see Goku (and Vegeta) totally leave them in the dust? Although the new transformations are a regular point of criticism of the revival era, it feels as though Toriyama has been pushing the protagonists in this direction for a while. Toriyama has lowballed the Super Saiyan multiplier forms to actually be inferior to the full potential of the regular plain old Super Saiyan. Then there's the God-like Saiyan form introduced in RoF, with which Goku and Vegeta can access godly power in their base forms. It seems that every time Goku and Vegeta attain new levels, they are being pushed to internalise the power they gain and reduce unnecessary baggage that comes with transforming.

I'm not suggesting that the regular Super Saiyan forms will ever go away. Even if Goku and Vegeta abandon them, there's still Goten, Trunks, Gohan (maybe), all the Universe 6 Saiyans and others who can bear the torch. The image of Super Saiyan Goku is so strong in pop culture that it'll always be included in games and merchandising till the end of time.
There could be some evidence for Goku's neglect of Super Saiyan. By the time he encounters Uub at the 28th Tenkaichi Budokai, he doesn't use Super Saiyan at all. Now, of course, the logical explanation would be that he simply doesn't need to use Super Saiyan on the amateurish boy especially now that he's grown so much stronger in the interim, plus he wouldn't want to freak the audience out. However, with recent revelations that Uub possessed godly ki thanks to inheriting the Dai Kaioshin's power from Buu (somehow... I've long since given up trying to make sense of how Buu's body works), it may be strange in hindsight that Goku didn't need to go in harder against him.
A counterpoint would be that in the probably-non-canon self-parody manga Neko Majin Z by Toriyama, set after the end of the manga, Goku does in fact use Super Saiyan while training against his feline pupil Z. Though again, it's a parody manga produced long before the full revival era was a twinkle in Toriyama's eye, so the likelihood of it factoring into current storylines is very slim.

We could assume that Goku has more or less completed his training with Whis by the time the 'Peaceful World' rolls around, so it's possible that he's mastered the ability to use Ultra Instinct in his base form. The fact that Uub still manages to damage Goku in this state will make his initially impressive showing against Goku from the context of 1995 look astronomical in 202X. Goku and Uub's fight is extremely short in the manga and expanded in the anime. In the anime, Goku doesn't look like he's fighting any differently to usual -- if anything he seems to fight more brutishly with a normal boxing stance rather than his classic Kamesenryu stance. It's all very exciting either way. Thoughts?



