In a new report from Dave Meltzer of The Wrestling Observer, they have reported what the current plans are for The Rock's involvement for WrestleMania 32. As of now, The Rock is not scheduled to face Brock Lesnar, as has been one of the rumored main events of the show. The Rock's scheduled opponent, should he be at the event, is Triple H.
The WWE's hope was that Ronda Rousey could compete at WrestleMania and she could take on Stephanie McMahon in a singles match, while The Rock could work one with Triple H. Another possible plan was a mixed tag match with the four, building off their angle at this past WrestleMania. The backup plan, i.e. the UFC not clearing Rousey to compete, was The Rock versus Triple H with Rousey in Rock's corner and Stephanie in Hunter's corner.
Rousey's movie commitments for early 2016 will likely keep her off the WrestleMania card altogether, but the plan for now still is The Rock versus Triple H. Like it or not, it makes sense to build off what they started and Rock/Brock could always happen at a later date. Keep in mind that The Rock has been injured in his past two matches and Triple H would be a far safer opponent for his health than Lesnar.