While WWE is planning on The Rock not being available for Wrestlemania 32 next year, the entire lineup would be reshuffled if that changed. Should Rock commit to working, the company would blow off Triple H vs. Roman Reigns at Royal Rumble but right now, as we reported earlier in the week, it's one of the planned main events for Wrestlemania.
A decision hasn't been made regarding the winner of the Royal Rumble. The current plan has Triple H abusing his authority and gifting himself a shot against Roman Reigns for the WWE World Heavyweight Championship while also "forcing" Reigns to face the Royal Rumble winner. The idea would be the "deck is stacked against Roman" and he'd be forced to defend the belt twice on the same show.
Another idea pitched is Hunter stripping Reigns of the title before Wrestlemania and "firing" him as well. This would lead to Roman vs. Triple H at Wrestlemania carrying the stipulation that Reigns had to win to get his job back.