He explained that, typically, original IPs end up having things cut from them in order to make release, and that these ideas end up being added into the sequel. This didn't actually happen with Wonder 101--nearly everything that Platinum wanted to put in the game, it put in the game. The only exception, however, came from the actual 100 heroes themselves.
While he said that he loves all of the characters in the game (he couldn't even choose the one he liked the most, they're all too precious to him), Kamiya said that, in the event of a sequel, he'd wants Platinum to allow the community to suggest ideas for super heroes to join the cast. There's no official way to do that, obviously, but when we asked him if he'd be alright if people tweeted him ideas (Kamiya is extremely active on Twitter), he said that'd be a great way to do it.
So, there you have it. You know what to do. Think up a super hero you want to be in the Wonderful 101 2 (should we just call it the Wonderful 102? Or is that premature?) and send a message to @PG_kamiya. Get to work!