You're stuck in this mindset like it's a hard fast rule.
Every generation has different parameters and conditions that have to be examined individually.
- Diminishing returns on silicon
- Increased costs for advanced chipsets
- Pandemic recovery
- Global economy
- The seeming discontinuation of Xbox as a platform in Year 5
- GTA6
- EA FC, Madden, and CoD all eventually going current-gen only
If Sony was sticking to the roadmap you think they are, the PS5 Pro would have come out in 2023 instead of 2024.
If you actually looked at the trends, each PS generation has lasted longer than the one before it, with PS3 to PS4, and PS4 to PS5 both being 7.
The PS6 won't come out until 2028 at the earliest. The PS Handheld will either come out next year or in 2027.