The Undertaker is said to still be pretty banged up from his match with Brock Lesnar at WrestleMania 30. There are people in Vince McMahon's inner circle that believe Vince didn't make the decision for Undertaker to lose at the last minute but he simply waited until the last minute to tell anyone. The belief in the company is that Vince made the wrong call but nobody can say that publicly even though that's what the majority viewpoint is within WWE.
Mick Foley, at a comedy show in Jacksonville, brought up The Undertaker's streak and people started booing. Foley said that he thought Lesnar was the perfect guy to end the streak but not because he was a former UFC Champion. Foley's thought was that whoever beat Taker would wind up with heat on them (I'm guessing heat from the locker room) but that wouldn't bother Lesnar since he's one of the few people that doesn't care what others think of him.