Far Cry might keep following the same formula, but I personally like that formula. Far Cry was amazing (except how long it was), Far Cry 2 was pretty boring honestly, but they ramped it up with Far Cry 3, and since then (just started playing FC4), it's still a fun series. I was able to play Primal for a while off my buddy's account when I built him a new computer and it was still fun.
So long as the games are fun, I don't care what formula they follow. Now, for GTA's sake, the games stopped being fun in lieu of "realism", starting with IV and V only made things worse. With San Andreas, you could do everything that made GTA fun in the first place and more, but with the introduction of the "realistic setting" GTA games, what we have is pedestrians calling the cops on us for standing too close to them. Or the peds attack us and when we defend ourselves, we get the cops called on us. Or you could be in the fastest car in the game and the cops can still catch up to you and ram you off the road. Or you can be in a freaking tank and the cops can still ram you off the road. Rockstar stopped making GTA fun, so I never bought GTA V after I played through the main story and if they don't change something drastically, I won't be buying any future GTA games either. Far Cry, on the other hand, if they made FC5 under the same formula they have been, I'll probably pick it up when it goes on sale.
Edit: The trailer on Steam (available for pre-purchase now) doesn't show much. It's suspiciously vague which tells me they don't want any specific protagonist for any story-related reason. They just want some no-name to come in and stop a cult for "reasons". Based on the trailer, I'll definitely wait until it's on sale. A big sale. Like 75% off kind of sale.