I think some folk need to lower their expectations a bit about the scale of the titles they think will be seen at the start of the next generation.
You can have all the huge cities and thousands of NPCS you want but the bottom line is that those cities and NPCS have to be costed out, designed, built and coded for by regular human beings.
The transition to the bells and whistles that the new generation will be fully capable of doing is not going to be an overnight thing.
And all the first party developers that would work on large scale games aren't releasing games for 1-2 years
InXile is winding down on wasteland... last release this year
Obsidian is just winding up on a project... last release last year
Initiative is unknown. There's things happening here that are confusing to most outside observers.
343 is doing cross gen Halo, as it was announced for Xbox One first
Coalition is just starting their next project... last release last year
Ninja Theory / Hellblade 2 is entering full development but it's not close
Compulsion is probably early in their next games development... though it's been 2 years since their last release
Playground RPG is entering full development and likely is still a year or so off
Like... we are fairly certain the next games coming down the pipe will be Forza and Forza Horizon. You could make a case for Horizon but they're already doing amazing stuff on current hardware.
It just seems to me the reason why there's going to be cross gen games is because most of the big budget releases aren't there yet.
We are expected to see initiative and playground RPG games announced (not releasing) this year. Compulsion and Coalition next year. Obsidian next year or year after. The rest are gonna be fairly random. Undead might be going AAA but we aren't sure about that but that would shift their project further back.
MS apparently has a few worldwide publishing games coming out but as to when they're coming is anyones guess... same with scope. We don't know.
So again. Looks like the main reason for this is simply because of what's coming out (Halo, Forza games, possibly worldwide publishing) which is more narrow in scope so they could work on Xbox One with graphical limitations. Convenience of portfolio timing more than anything.