Considering that he was World Champion at the time, one might have assumed that Seth Rollins' injury would have sent WWE officials into panic mode trying to figure how to change the plans they had and reorganizing his WM32 Main Event match. Well, that assumption would have been wrong.
According to PWInsider.com the reason there was no panic in the organization was because the WWE's plans for the World Title heading into WM32 didn't have much to do with Rollins actually.
Sure, the plan was to have Rollins lose the title to Roman Reigns at Survivor Series or soon after, and that singles match obviously is out of the question - but that is really the only big thing that had to change.
As far as their longterm plans heading towards WM32 and the main event matches, well it is being said that Rollins' injury caused very little shake-ups there either.
The WWE had 3-4 main matches set and none of them have needed to change due to the injury. And from that I think we can deduce that Seth Rollins wasn't originally scheduled to be in a WM32 main event match even before he got hurt.