All in the past again here is the future. God of War, gt 7, Horizon 2, ghosts of Tsushima, ratchet and clank, Spiderman 2, last of us of us remaster ect.
It makes perfect sense for Sony to make sequels to existing successful IP. Only a moron would say to themselves, "well we've spent several years and tens or hundreds of millions of dollars to take a chance and build this new IP that's turned out to be very successful... now let's throw that all away and build something completely new just for the sake of it!". That makes no sense.
Regarding the subject of new IP and your apparent feeling that they won't be doing that, please remember that absence of evidence is not evidence of absence. Just because they haven't openly talked about big new IP to come doesn't mean they're not going to be doing it. Within the past year we've seen new IP like Dreams, Ghost of Tsushima, Destruction All-Stars, Iron Man VR and Returnal. We don't know a great deal about future IP yet because we only have a small window into their future plans but so far this is what we know or is rumored:
- New IP with Haven studios
- New multiplayer IP with Firewalk Studios
- Cory Barlog is rumored to have a second team at Santa Monica Studios working on a new IP
- Naughty Dog are in pre-production for their next big project, which could either be a new IP or TLOU3, we don't know yet. This is why they've got the bulk of their workforce working on Factions 2 and TLOU Remake, because all of those people aren't needed during the pre-production phase of their next big project. It allows them to keep their employees busy and employed during this transition period
- Bend studio is rumored to be working on a new IP as per Jason Schreier
- Remedy is rumored to be working on an exclusive for Sony, so there's a high chance that's a new IP
- Guerrilla are rumored to have a second team working on a multiplayer based project. We don't yet know if this is a new IP, or a MP mode for Horizon Forbidden West or a revival of an old IP like SOCOM.
That's just a tiny window into what they are and what they could be working on and there's a lot of new IP involved in just that tiny window. There are likely plenty of additional partnerships that we have no clue about yet. This doesn't even take into consideration all the new VR IP we're likely to see next year with the release of PSVR2. So no, we're not just going to get sequels and remasters. Be patient and let them show us what they're working on in their own time.
Edit. Oh and Housemarque may have another game in the works for Sony going by a job posting that was shared by an XDEV rep. Also Arrowhead are rumored to be working on a new AAA game for Sony that could be a new IP. Supermassive had previously stated they had a few exclusives for PlayStation in the works, but we don't know if that's still a thing or not.