Look, the PS5 aint coming in 2021. It will be out by 2020 latest.
Gamescom and PSX are gonna be smaller scale stuff. Maybe SCEJ stuff too (since they dont always use TGS). There is no way any internal studios will have major releases out by 2019. 2020 earliest and by then its PS5 season.
MediEvil had a teaser at PSX with literally nothing to show. Gamescom was the more likelier event to see it again. After all Sony needs stuff for GC and PSX. If anything, I am surprised they didnt hold Tsushima back too, but seemed like a good call. The showing was really good.
This is in hindsight, but it was a mistake for Sony to announce it during PSX. They should have reiterated to fans that PSX would be very very low key and do not expect new announcements, and saved MediEvil for E3.