[Guyver Spawn]

It could be that Goku in his base form because his base form is much stronger now since he has god powers. Toriyama mention in a recent interview that Goku realized that mastering his normal state and Super Saiyan would raise his level more and sap less strength. So that he probaly not going to use SSj2 and SSj3 again anytime soon.

Quote:

Q: 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…?!

A: 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.

http://www.kanzenshuu.com/translatio...buu-mysteries/