To be fair to them an extra two years, if it is that much, gives them the chance to pack more powerful HW, but by the time enough devs take good advantage of that power PS6 might be around the corner.
It depends on the cycle, 5-6 years is not enough for a meaningful next-generation upgrade I think. It was not last generation and each new generation the time for next gen increases (we have yet to see a semiconductor breakthrough to buck the trend: it is taking longer and longer for each new meaningful semiconductor node update and designing / manufacturing on the new nodes is also getting more and more expensive to design on them… I think at 5nm with EUV you also hit a quite hard limit in terms of size at around 400 mm2 so you need to go chipset or constrain your size).