Ok because i keep seeing people on here saying 20 and thats it, supposedly Omar said 20 is the launch roster which is fine. but people need to stop acting like its the final. Omar said himself Superbot will always keep trying their hardest to get all the characters people want.
There was a completely separate question where he was directly asked about 20 characters: I wrote down directly what he said to several questions here: http://m.gamefaqs.com/boards/668999-playstation-all-stars-battle-royale/64243351
Here's the question and his response:
How many characters will be in the game at launch? "Our launch roster is 20 characters. The 20 characters available today in this demo are the characters that will be in the game at launch."