The big issue isn't about resolution but about processing power and how to handle memory. I think the lesson from the current generation from a developer point of view is that it's better to be overpowered in the beginning than to hit hard technical limits a few years into development. Both Xbox One and Playstation 4 got more powerful upgrades to general confusion and dismay among gamers, who felt that when they purchase a console, unlike when they purchase a pc, there's an understanding that the hardware won't need upgrades for the rest of its lifespan.
You saw the contrast on game level very clearly with Skyrim, which got a massive current gen upgrade. I think to the average person who didn’t play it the difference on surface level might not have been that big between the original game and the Special Edition, aside from the obviously higher resolution of textures, but to anyone with any form of insight in modding and coding - and thus to the developers as well who were still creating DLC - the switch from 32-bit architecture to 64-bit architecture was like night and day. Skyrim was still brilliant when it came out and was a huge success, but if Xbox 360 and Playstation 3 had had better base capacity it might have turned out a very different and much more stable game, with bigger and more animated cities and a game world that felt more alive. We might also have had user-created mods on consoles seven years earlier with everything it entails.
I imagine massive game worlds will end up being a big thing again next generation; you've got Star Field and a new Elder Scrolls coming out and almost certainly a new Fallout, a Witcher and a Grand Theft Auto too, and there are bound to be a bunch of new IP:s too. All in all I think singleplayer experiences will come back into focus in a big way, and they will put high demands on the hardware.
