Just like these, popular fandom imagination or question we've all wondered (what if Boo had absorbed someone else, what if Cell had absorbed someone else, what if Yamcha and Ten Shin Han had fused, what if Raditz and else turned into giant apes...) will probably be the inspiration of several new what-if characters in sequels/DLCs.
And don't worry about seeing a Super Saiyan 5: I don't think they'll ever do that, because it's not based on anything existing, they wouldn't invent a transformation from scratch or from fans' crazy imagination, it would lead to a mess and be obviously going too far (if they did, then why not Super Saiyan 6, 7, 8, 9...).
I think they're mostly making a "transfer" for transformations that were meant for another character, like "what if A had gone through the same transformation than B?": they did it with the giant apes, with the fusios, now they do it with the Super Saiyan 3...
Next stop Super Saiyan 4 for Gohan, Trunks and Goten? Hum, not sure, since it is often said that only pure-blooded Saiyan can go there, so it would be a risk to offend fans with something that is widely said as being impossible...
Super Saiyan Raditz, Tullece and Nappa are more likely (they wouldn't have to worry much about Nappa's hair at least...
And having a separate character for what-if transformations could be the right way not to offend fans: I think most of them want to play with the characters they know from the manga and TV shows, meaning the original Vegeta who never went Super Saiyan 3. If they played with the regular Vegeta and he could become a Super Saiyan 3, they might not feel like they're playing the REAL Vegeta. That's my guess anyway...








