Butler might not be true. I say that because we only know the other three thanks to this.Here's something interesting, guys.
http://www.gametrailers.com/side-mission/2012/05/18/cole-mcgrath-nathan-drake-snake-and-kevin-butler-would-seem-to-be-in-the-ps-all-stars-battle-royale-cast/
Just so you know, if at least the "Kevin Butler" part happens to be true, I'm going to main him, no questions asked.