That is not how game development works. When you start producing a game the team sets a goal, thinking about what target to hit in terms of visuals and richness of game features and the scope of the game world. In some games like red dead redemption, 60 FPS is something that is nice to have, but developers also want to push the graphics to such an extend that its visually stunning. Thus you have to decide, do I let this game run at 30 FPS with higher graphical fidelity or do I push for 60 FPS. Cross Generation Games will most definitely run @60fps minimum. True next gen titles on the other hand where 60 FPS is not needed, like e.g. open world story games could very well again run @30 FPS, to push technology as far as possible. Also for as long as I have been in the industry, what I was taught is that games are always developed for the weakest systems, sure the next gen consoles are very strong right now, but in a couple of years they are again going to be mid range. By then in order to further push games 30 FPS could again be the norm. But we shall see, for now it all looks very promising and the next gen consoles are stronger then ever.