I would say Sony should get at least two 1st party titles ready for launch and save the others for later. You want to have something between the Vita's launch lineup and the PS4's launch lineup in terms of quality and quantity. My guesses of what the PS5's launch titles will be are:
- Keiichiro Toyama's (Gravity Rush series) new title - Gravity Rush 2 was released in January 2017. A late 2020 launch will give Toyama nearly 4 years.
- Gran Turismo 7 - GTS has provided a solid foundation and Kaz Yamauchi doesn't need to start from scratch nor switch to a different architecture.
- Horizon 2 - A late 2020 launch will be over 3.5 years removed from Horizon's launch and 3 years removed from The Frozen Wilds' launch. I don't expect it to be out when the PS5 releases, but an early 2021 release date is likely, imo.