If PS4/XB1 can life along Pro/X, so will Lockhart along Scarlett be able to - 4K rendering and 4K textures DO require a significantly more memory/bandwidth, so if MS is about to make a let's say a FullHD next-gen console, they can easily cut the GPU size and bandwidth in half compared to Scarlett
I mean, I played Witcher 3 on both 980 and 1080Ti, 1080p60 and 4K60 respectively, and guess what? It was the exact same game. Same CPU, same RAM, same SSD, the only thing that changed in my PC was the GPU that had more TFlops and more vRAM/bandwidth, nothing more, but the thing is - even in 1080p back on that 980, it was still the same Wither 3 we all know. And that applies to every single game out there, I know most of the kids on gaming sites love to fight about pixels in their console wars, and the media live off those wars, but the games are all the same, no matter the output resolution, that's a fact. Let me put it this way - running Life of Black Tiger in 8k 120FPS won't make the game any better, at all.
Like i said earlier today in the other topic, I have a strong feeling the lazy devs will try to sell us as much fancy gimmicks as possible, including eye candy (or should I say mostly eye candy), instead of actually focusing on making great games - games with engaging stories, interesting characters, and great/fun gameplay.
RDNA's 4TF is really close to the same computing power as GCN's 6TF found in X1X ofers, which can do even such a demanding game as RDR2 in native 4K for example, so there's really no excuse if they would get such computing power for much, much lower resolution, especially given all those dynamic/temporal/reconstructed resolution tech the devs have developed during this gen. "Significantly less RAM: could mean 8-12GB vs (most likely) 24GB in the "big" consoles, which again, shouldn't be much of an issue, as MS already separates 4K content only for the X1X - as far as I know you simply ca'nt download 4K textures on the base XB1. And again, if the devs can already make pretty much infinitely large levels with 8GB of RAM on the PS4/XB1, such amount shouldn't be much of a bottleneck, given it would be backed up by the supposedly marvelous new SSD tech.
All in all, I'd love to see a cheaper, FHD-focused console, but A) MS must be smart about it, and not cut the corners by too much - soma rumor says about Lockhart targeting QHD, which IMO would be a dumb idea as no TV support such resolution natively, which would only unnecessarly waste the console's limited resources, and B) the devs would have to stop whining and get the job done, but - if such a console would really appear, and would be successful, they wouldn't have a choice i guess. 2020 gaming conferences will surely be hella interesting, that's for sure.