If you look through the winner of the Rumbles then only really Vince sticks out as being a suprise.
Its not something they usually suprise people with.
I think whats tough this year is its entirely possible that both Current champions wont walk into Mania as champions. I still think that probally Cena & Batista (or at least one) will end up as champion come Wrestlemania.
I'd still bet on one of Jericho, Edge, Batista or HBK to win it. For HBK it might be the only way for him to get his rematch against Taker.