I actually could see any one of those guys holding the main title over their shoulder, I don't think there has ever been a stable as talented and as solid as these guys in years, possibly since The Four Horsemen, which is why I'm glad WWE have pushed these guys as much as they have done and continue to do so for a while.
People are saying Reigns, due to his look ... and it's very possible Reigns could get it first, the only thing about Reigns is he's too quiet on the mic, he's more laid back than Orton, which I think they may want him to have a bit more personality with, Seth Rollins always reminds me of a Jeff Hardy, not afraid to put his body on the line and taking the high spots, his performance skills alone earn him the belt and he's pretty solid on the mic, as is Ambrose, who I feel is the best out of the three, his psychology is unreal also and his mic skills are fantastic, all three of them can really work a match too and tell a story, so it's hard to say.
Good question none the less, it makes you think
