2021 would imply CPU cores strong enough, even in lightweight versions, to both deliver a new gen-worthy performance leap and allow a hybrid version too.
But once the CPU tech is decided (and it can be done also before AMD actually releases it, if that tech already has advanced enough in the roadmap) it could also happen that Sony launch the home version in 2020 and the hybrid one in 2021: Zen 3 is planned for a 2020 launch, but its full range could take time to be wholly launched.
Zen 5 is totally out of question even doing the first launch in 2021, while a 2019 launch instead would force Sony to use Zen 2, and this would make both a hybrid version and achieving a good performance leap from current gen quite more difficult. Not to mention that launching in 2020 or later VR tech could already be mature enough to become mainstream, and even entry level console HW could support it.
To conclude, while a 2021 launch could seem quite late to some gamers, it would make a lot of things a lot easier.







