I still contend that price cuts being fewer in number and lesser in degree than they were in Gen 6 & earlier is why PlayStation & Xbox systems are able to run on longer generations than the previous norms. Last generation it appears to be the culprit behind slow growth and delayed peaks. Essentially, last generation was as long as it was on purpose, and probably for good reason (imagine how much weaker the PS4 & XBO would have been at $400 had they launched in, say, 2011).
This generation, it's basically been keeping non-holiday sales steady, but not producing any clear longer-term growth, with official short-term holiday price cuts diverting a larger portion of sales towards Q4 than in prior generations. Outside of Nintendo systems, you don't see the early peaks you used to anymore, and it remains to be seen if even Nintendo will still run on shorter gens than Sony & MS, or if they too will attempt to put the Switch's sales on a PS/Xbox-style "slow burn" sales trajectory.
Yeah, I think this is a factor too. There are several factors.
Although I'm still not convinced Sony will release the PS5 after 2019. One reason that the last generation was so long was because Sony backed themselves into a corner by making the PS3 so powerful (and consequently really expensive). IIRC correctly, the PS3 came down to $400 in 2008. So that is only a 5 year gap between the PS3 at $400 and PS4 launch of $400 in 2013. Once you account for the huge price of the PS3, it actually didn't take them an unusually long time to release PS4. The unusual part was actually the high power of the PS3 when it was first released.