Yep. Gameplay mechanics and control input! Let's have one gen, or even half generation, of no compute/processing changes, but rather new innovative control devices which can enable new gameplay mechanics.. That's an area where gaming could advance drastically, and at the same time not break the bank for dev studios.
Not even limited to just that. Let's look at dramatically enhancing audio. Give the audio guys their time to shine. Let's look for new ways to improve game presentation. Meaning, innovation in dynamic camera systems, innovation in user interfaces, and so forth.
There's tons of potential improvements in so many other aspects of games which could really invigorate game design without the massive gen-on-gen cost increases.