I definitely see Ryback winning the Rumble. In fact, it'd be awesome if it came down to Ryback and Cena in a big face-vs-face confrontation that ends with Ryback tossing Cena out (to a big pop), similar to Cena/Batista at the 2005 RR. (Cena's motivation to win the Rumble is he says he wants one last shot at Punk - or one more shot at The Rock as the case may be - at Wrestlemania, depending on whoever wins the WWE Title match that night, so he enters the Rumble.) And my prediction is that he goes on to win the WHC at Wrestlemania. The champion will probably be Big Show at that point. They can book Show as a credible monster heel from here to then (they're already off to a fresh start with him beating Sheamus fairly) and then have Ryback be the one to finally crush him.
They'll have to think of some sort of exit strategy in regards to Punk keeping the title but Ryback still remaining the dominant one, because that's the only logical way to go at this point. If they were gonna have Punk drop the belt to Ryback, it would have been at HIAC, so it's obviously not happening now. I also doubt he and Punk will fight again at TLC (rumors say it's gonna be Cena/Punk) unless they pull the '99 KOTR ending where someone raises the title from Ryback every time he reaches for it. But Ryback/Punk is done for by the time the Rumble gets here, for obvious reasons.