I am not sure why everyone is just assuming that Undertaker vs Punk at WM is a given.
The way Cena talked the other day, I have a suspicion the Rock/Punk rematch will be mired in controversy, to where the WM main event becomes a triple threat match: Punk vs Rock vs Cena. Punk deserves a high profile match at WM, not being stuck in some silly feud match with the Shield or Ryback or something like that.
If Undertaker really is too broken down to wrestle this year, then I think HHH/Lesnar now goes without saying. I suspect they would like to have done Undertaker/Lesnar if possible, but with 'Taker hurt, they can just slide HHH back into that spot and let him get revenge for his loss and for the attack on Vince.