i imagine insomniac's lineup of games look something like this (other than the VR titles that are probably going to be new IP/ports to PSVR and their release schedule are too unpredictable):
new ratchet (if its actually a PS4 game it will release in the summer/be cross gen)
spiderman 2 (around september 2021, 3 years after, spiderman 1 full development took 2 years according to insomniac and a sequel means less pre production time)
new ip by ratchet team (2022/2023, might be more if new ip)
spiderman 3 (after that spiderman games on hold probably) (fall 2024, same reasoning as Spiderman 2)
sequel to the new ip/more ratchet depending on the success of the new IP
after that who knows, maybe spiderman team will tackle another Marvel IP, or a new IP.
this is a very strong output imo. of course stuff could go wrong in development and delays to take place but insomniac have been one of the best studios in terms of development time efficiency (and at the same time, minimal crunch! even jason schreier corroborated that)