Ghost of Tsushima launched in 2020 so 3 years ago and so far they haven't announced a new project. It being a high profile game I doubt they are going to release it 6 months after the announcement. Same goes for Days gone Dev. Days Gone was released in 2019, so pretty much 4 years ago.
TLOU MP, we still got nothing more than some artwork. As for London studios and Media Molecule, they where also no shows. I can give MM some leaway, but London Studios last game was released 4 years ago and they tend to make VR games.
So even if those studios (Sucker Punch, Bend, London Studios) all release a game next year which is doubtful at best. We would already be 3.5 years into this gen.
I doubt those studios can suddenly release games much quicker (within 3 years after their first release assuming PS6 is announced somewhere in 2026/early 2027) after their first PS5 release. Only ND might have enough manpower to do so.
None of that indicates development hell though.
I mean, outside of Sony Bend who faced internal strife, and Media Molecule who was supporting Dreams until this year, these timelines for London Studio and Sucker Punch's next games make sense. I also wouldn't rule out a Fall 2024 for the GOT sequel, it could very well get a tease at a SOP, or even something like TGA, with an extensive showing next year.