Don't know where else to put this, but I think it's probably fairly relevant here. I read on Bleacher Report where someone said that there needs to be a bigger reason for Punk to want to take on The Undertaker. I somewhat agree with this, as Punk would be a different kind of Streak match from the ones we've seen in the last 4 or possibly even more years. The last two were also against people already at the end of their careers, and it needs to be refreshing if Punk is to face him.
One idea I have thought of, is for Punk to argue that he can beat The Undertaker regardless of when or where, with Undertaker challenging this suggestion, and for one of them (kind of does not matter who) to challenge for a match on Raw sometime before Wrestlemania. Despite being a heel, my idea is for Punk to have a completely clean win, over a seemingly strong Deadman. Undertaker not only needs to look good to make it seem legitimate, he needs to look almost unbeatable, and for Punk to either a quick roll up pin for 3, or a GTS out of nowhere, stunning Taker, but kicking out, and for Punk to control the next 5 minutes of the match, resulting in another GTS for the win. Undertaker could get enraged, make his hilarious face he made over Shawn Michaels when he kicked out of a Tombstone, while Punk rushes out of the ring before he sits up.
It could be left at that, and then the next week, Undertaker could cut a promo, saying that Punk is good, but everyone knows Undertaker brings himself to a whole different level at WM, and that he can still win. Punk comes out, and reminds him that Best In The World, means Best In The World, reiterating that it doesn't matter where they fight, Punk is now BETTER than Undertaker. Punk, out on the stage, Undertaker in the ring. Taker looks over his shoulder to the WM sign hanging down, then looks back at Punk, and sets it up.
Of course it won't happen, but that's my fantasy way of it playing out.