If rumours are to be believed, then Punk is facing HHH at WM, so unless HHH wins the title in the next month, it's unlikely that Punk will win the Rumble. Basically, whoever wins the rumble will job to Cena, so it'll probably be Roman Reigns, he's hot right now, what better way to kill his momentum than have him get buried by Cena. Look where Miz, Ziggler and Sandow have ended up after facing Cena.
My personal choice to win the rumble would be
. When you have a wrestler as over as he is right now, you have to use him, him winning the rumble to set up a showdown with
would be good for business. Cena's a guaranteed draw (for reasons unbeknownst to me), and Bryan will sell merchandise, the pair should get good buys for WM30 for that match alone.
However, if Bryan is to face Cena, he'd have to turn heel. Enter the Wyatts.