WWE could make a good storyline of Cena winning Beat The Clock, choosing number 1 to win legitimately and throw over 29 other men, but being the last man eliminated to lose after trying to do the right thing, leading to a slow heel turn.
They need to do something to freshen up Cena's character.
Knowing WWE though, Cena will do all of that except get eliminated last. He'll win.
I expect Cena to win and pick 26th position, which I think is statistically the most likely to win the rumble isn't it? It's somewhere around there I think. This way they still have the 30th spot for a good surprise, Cena doesn't look like he's taking too much of an easy way out by coming out 30th...and he will of course win the rumble.