That would explain why they had Lesnar hit McMahon with the F5 at the end of SummerSlam. Part of the reason why they are booking McMahon vs. Lesnar likely has to do with McMahon being a ticket mover during the weeks leading up to the match with The Undertaker for WrestleMania 32. Ticket sales picked up when he returned and when it was announced that he would face Taker.
As previously noted, the match at Survivor Series between Lesnar and Bill Goldberg is being considered a "one and done" match and, as of right now, there are no plans for Goldberg at WrestleMania. Something tells me that they will change their minds on that. I believe the plan is also to do Seth Rollins vs. Triple H at WrestleMania. That was the original plan for WrestleMania 32 in Dallas before Rollins went down with an injury.