Yeah. Let's pretend NES and SNES and N64 and GC never happened, and that Nintendo's audience hasn't been enthusiastically accepting the next wave of better graphics, and let's instead imagine that Wii is the only console Nintendo have ever made and that it is the best selling console ever (which it's not, at 2/3rds PS2 and ~ PS1 numbers) and more people didn't want to buy the same console with better graphics than something new (PS360 sold more than Wii). Clearly, then, better graphics is a dead end and consoles can only thrive on some new something.
While Nintendo releases outdated hardware once again? How's about you change your argument to be platform agnostic, and just ask what it'll take to get a certain level of performance beyond PS4?
Quite possibly not as long as before. It depends on the price target of course, as a monster machine instantly gains 2-3x the performance even on current tech. Add in new-wave tech like HBM and stacked processors, a next-gen leap probably isn't dependent on lithographic processes.