Re: How much longer will Punk be WWE Champion?
It would be huge for Punk to hold the belt through the Rumble match with the Rock whereas winning the belt won't do anything for the Rock or make the Rock's Mania match any bigger. If Punk holds the belt up until Mania and they do Streak vs. Streak, Taker winning the belt wouldn't make sense because it would likely be his last match, he won't be a full timer even if he does come back again eventually, and again winning the belt won't do anything for him.
If Punk can beat the Rock and then end the streak, he becomes a mega star that's on Cena's level if not above Cena (having held the belt longer than Cena ever did, beaten the Rock when Cena couldn't, and as the only man to beat Taker at Mania). If a young guy (most likely Ryback) beats Punk, the new ultra mega heel, for the title later this year, that guy gets a rub that's bigger than any other win could give him.
That said, Rock will probably beat him. I fully expect people to say that Taker should never lose at Mania, and I respect that opinion since the man is a true legend, but I don't think any one person is bigger than the business and I think there's too much value in letting the next generation get big wins over older guys.