The thing is the average consumer doesn't care about the cost of process nodes going up or their being major engineering challenges, they expect something for their money. If PS6 is highly iterative and just something like a 3nm monolithic chip with bump in CPU/GPU architectures and no more than 60% more raw power over pro; then paired with another excessive cross-gen period it'll end up as little more than a PS5 Pro+. I think a significant number of people will just hang around on PS5, it already has the drastically improved load times and general responsiveness / quality of life improvements.
I think they need to find some way to pull a miracle out of their arse as there needs to be some self-evident leaps on screen to make it worth it on this go around and not someone saying "if you look closely, you can see the ray tracing on this surface here, it's really impressive what we're doing here because the calculation is really complicated and it's being accelerated by special units, it's running at sub-1080p and the particles look like tv static, but it's really impressive cause of the calculations, honest...".
I feel like they got away with it this gen, but I wonder if they get away with it again. I just don't see significant chunk of people being inclined to switch again to what'll probably be a $600 console (before a disc drive) so they can play what are fundamentally the same games with some extra bells and whistles. I think they really have to find a way to wow people or to differentiate the experience somehow. I know totally exotic setups are out of the window but I feel like they need to find a way to lean parts of the system towards that again to punch above their weight and at the same time make it incredibly easy to utilise, they also need to drop a few experiences that simply cannot be had on PS5 or even PS4.
Many people I know are frustrated with things as they are and I've explained to them as clearly as possible why things have slowed and how process nodes effect that; and to paraphrase their response it's basically "ok, I get it, but that's not really my problem, I expect a certain step up for my money and they need to find a way to do it, if not then I'll wait and buy a PC down the line, just not bother anymore or stick with my current console for most of the generation".
They [console makers] have to find a way.