I agree the Bryan/Wyatt feud could go past the Rumble and into the Elimination Chamber PPV. I could also see it just as well ending at the Rumble, though. Definitely won't drag out till Mania.
Batista and Lesnar is certainly a possibility and makes too much sense not to happen at some point (although nothing says it has to happen at Mania.) I made a thread about this recently so I'm basically just repeating what I said there, but it's a dream match of sorts and Batista has said recently that should he ever return to the WWE, Lesnar is the man he would most want to have a match with. And look at the way Lesnar's being booked currently - breaking the arm of "The World's Strongest Man" and going over (as we all know will happen) "The World's Largest Athlete" at the Rumble. He's running through all the biggest guys in the company and it's making me think that it's all gonna lead to Batista stepping into his path and proving to be the one big guy that Lesnar can't just tear through.
One way of setting this match up is to have Lesnar pull double duty at the Rumble by having The Authority tell him on Raw that if he wants a title shot, then he'll have to earn it like everyone else by winning the Rumble. So he goes over the Big Show and then later enters the Rumble and tears ass through a bunch of people but then Batista's music hits (I'm expecting a big ovation on that one... I also expect that this would end up being one of the iconic Rumble moments that would be played back for years to come) and after some back and forth, Batista tosses him out. Later on, Lesnar re-enters the ring and hits Batista with an F-5, allowing someone to seize the opportunity to eliminate Batista, ala Goldberg in 2004. And thus the seeds are planted from there for a battle of the two monsters at Wrestlemania (The Beast vs The Animal is a great moniker for the match.)
IMO though, Lesnar/Undertaker is what will go down, which I have no problem with since Batista/Lesnar can always happen later whereas Lesnar/Taker mainly holds interest at the moment because of The Streak (even if we all know Lesnar won't win), which is only on the line at Mania. Batista will likely win the Rumble and defeat his former Evolution ally Orton, which I have no problem with happening either.