not to forget about the development cycles of new titles etc.
if you were to create new and ground-breaking architecture for a high-end console and then spend few years creating titles for it... it would be obsolete by the time you'd finish...
red dead 2 was 8 years in works - so the guys while not exactly sure what performance would the new gpus have - could assume that their game will work because the architecture of new gpus would stay more-or-less the same... just faster
I can't see a new console shipping at £800, but if there was a version of the standard console that simply played the same games but all at much higher resolution and frame rate and eye candy, then I would be tempted. The PS4 pro only tickles the edges of this idea.