I'm all in favor of a higher frame rate over graphics if a choice must be made. But that is something that I consider when playing on this generation of machines. I find it a little concerning when they make that statement cause it implies (and I hope I'm wrong) that "our system while more powerful is not going to be that much more powerful, therefore we need to assign a priority between frame rate and graphics.
I would imagine next gen should be capable of 4K60 at all times. But if a choice must be made I'd be ok with 1080p 60fps as 1080p is actually good (No once can honestly say: I can't see details on this 1080p picture)
But if 1080p then I will not accept a single drop in frame rate, whereas an occasional frame rate drop on 2160p could be forgiven (No more than occasional though).
I'm in the zone, don't bother me!