To answer this question I think you need to ask another question first. Has the WWE championship meant much since Punk has had it?
My honest opinion is no. Heading in to WM and Punk is in possibly the third biggest feud at the moment. And that is only because Jericho has come back for a match. If there was no Jericho he would be defending against someone else lower down the card. Which isn't Punks fault it is the roster being weak. The main two feuds at Mania won't even involve a belt. Punks match will probably be third last. The only other time I can remember the WWE title not being in the last match was the Taker vs HBK match.
My personal view is that the Cena vs Rock match should of had the title involved like it was supposed to. Cena should of gone into Mania with the belt. It would of meant so many possible changes could of happened. For example he could of cheated and retained the title turning him heel in the way HHH used to be. Saying that all that matters is the title, not what the fans think of him etc as he couldn't care less. Then on RAW Rock beats him in a no title match and Cena beats him down afterwards with a chair or something. It could make Cena the biggest heel since Hogan did it.
Or Rock could win and become champion again until the next ppv. That would be awesome.
Point is the title should mean something, and under Punk is has not meant much. He is supposed to be the top guy but is nowhere near the top. The title should always be in the main event in my opinion.
Punk's run has gone on so long that it has been difficult to bring others into the title picture and have them as a credible threat. But they need to start building up these guys fast because after Mania Taker,Rock,HHH,HBK,Jericho will probably all be gone for a longtime again. That is when we will see how weak the roster really is.