WWE apparently want to have someone better Punk's 434 day reign as WWE world champion. This sounds believable to me because of the way Punk exited and has spoken about them since. WWE management are petty enough to want to have someone surpass one of the key accomplishments of his career. Lesnar's already got a good start on that and him coming out of WrestleMania 31 as champion, and not moving on from WWE, would be a shock. Everyone expects ‘The Beast’ to lose the title and-or leave, with everyone focusing on Reigns beating him or Rollins cashing in on him (or both). Nobody seems to be speculating about Lesnar making it through ‘Mania and the following night’s RAW as champion.
|Could Lesnar hold the gold until 'Mania 32?|
If he managed that he’d look legitimately unstoppable. Yep, even more so than he does now because now we’re still expecting that Rollins or Reigns victory. He could retain and then stick around to do rematches with Reigns and Rollins, have that much anticipated match with Daniel Bryan and perhaps even work with guys like Dean Ambrose, Dolph Ziggler and Bray Wyatt. Were Bray to defeat Undertaker at ‘Mania 31 then a battle between he and ‘The Pain’ could be a big deal. They’d be the only two men in history to have defeated Undertaker at ‘Mania.
Lesnar retaining his belt into April would also create a good 'Mania to 'Mania story for Reigns: after failing to fulfil his destiny and beat Lesnar for the belt he could get depressed and turn heel. After a few months of being booked as a beast who hammers people in five minute matches he’d probably be embraced as a cool heel, allowing WWE to set up a face turn for him for the end of the year (maybe in a meaningful match at Survivor Series, to keep the importance of that event ticking over). Come next January he could vow to win the Rumble again and do it.
During all of this Lesnar could keep the championship and work with the Bryans, Wyatts and Cesaros of the roster. WrestleMania 32 would then be a rematch from the previous year’s show between Reigns and Lesnar, with Reigns having reinvented himself as a juggernaut and Lesnar having held the title for 595 days and not having been pinned since Triple H beat him at WrestleMania XXIX. Reigns could then dominate Lesnar in a ten minute main event to finally win the WWE world championship and set himself up as the replacement for John Cena.