The spec leaps will always continue to slowly decrease until some kind of new tech is available other than silicon. They are worthwhile however, based on the newest available tech at that point in time, for a reasonable price. This is another reason for the mid gen refreshes. Getting customers used to this now and not expecting huge increases like before, are necessary for the hardware gaming companies going forward.
Just look at the performance leaps and launch gaps based on approximate performance of PS consoles.
PS1 0.2Gflops, PS2 6.0Gflops, PS3 225Gflops, PS4 1850Gflops, which leaves you with:
PS1-PS2=30X (5 yrs NA)
PS2-PS3=38X (6 yrs NA)
PS3-PS4=08X (7 yrs NA)
PS3 should never have been as powerful and expensive as it ended up being at launch. It should have been closer to 125Gflops and $400, which would make more sense based on console hardware history. Apply that and:
PS1-PS2=30X (5 yrs NA)
PS2-PS3=21X (6 yrs NA)
PS3-PS4=15X (7 yrs NA)
The next theoretical jump from PS4 to PS5, based on this more reasonable "125Gflop PS3", should put
PS4-PS5=11X (20350Gflops) with an 8 year gap and launch date of 2021.
If PS were to actually try for a 2021 PS5 launch, 4 years from now, with solid 7nm and possibly 5nm in production, on top of new CPU/GPU/APU advancements, a 20Tflop PS5 console just may be possible. Whether it can hit $400 is another story. It may end up $500, but by then with inflation, that may not seem too much, considering we've already seen a 2013 and 2017 XB console launch at $500.
Whether PS wants to try and ride Pro out until 2021, or launch a "PS4k" to bridge the gap between Pro and PS5, or flat out launch PS5 earlier around 2019/2020 and just deal with an even smaller performance leap once again, we can only speculate. Based solely on the numbers though, if PS were to follow "what PS3 should have been", they would most likely be able continue the same hardware trend they have been since PS1.
The more I think about it, based on the locomotive of greatness that is the PS4, I'm starting to think a 2019 E3, PS4k reveal/launch at $400, with a 9Tflop performance spec is quite possible (based on 7nm and PS4 tech). Then launch the PS5 (20Tflop) with new tech, late 2021 for $500, or 2022 for $400. XB1X should be able to last another 4 years, so a 2021 PS5 just seems to make more and more sense.
PS1 - ! - We must build a console that can alert our enemies.
PS2 - @- We must build a console that offers online living room gaming.
PS3 - #- We must build a console that’s powerful, social, costs and does everything.
PS4 - $- We must build a console that’s affordable, charges for services, and pumps out exclusives.
PRO -%-We must build a console that's VR ready, checkerboard upscales, and sells but a fraction of the money printer.
PS5 - ^ -We must build a console that’s a generational cross product, with RT lighting, and price hiking.
PRO -&- We must build a console that Super Res upscales and continues the cost increases.
