What ammount of PS5 games do you think will actually use 4K/120?
Which ones will actually use HDR?
Will the HDR work while using VRR or 120hz?
Sony's own tvs don't even have proper Dolby Vision.
Will the HDR support from the consoles conflict with HDR chip in your tv?
HDR was already executed quite well on the Xbox One X and PlayStation 4 Pro starting with Assassins Creed Origins and Forza. I suspect that nearly all big releases will support HDR in some form, considering they already do on PS4.
4K/120 is a different beast. 4k/30 or 4k/60 will be more common for single player games. I've never had an HDR conflict on the console or streaming side.
The only issue is indeed support for certain standards but there's not a whole lot of Dolby Vision content out there. Most is HDR10 or HDR10+. Most Dolby Vision stuff is on Netflix and it's all TV shows.
You are right that there are lots of 4k blu-ray's not 4k, like Marvel and other heavy CG films, simply because they didn't render the CG in 4k.
You'll find that most movies that rely less on CG are native 4k. For me it has certainly been worth the investment for some of my favorite films.
Prices are also starting to come down a bit.
I have a 120hz IPS PC monitor but honestly I never thought that was such a big deal. The biggest benefit is less lag for competitive gaming and very fast games like racing titles or something like DOOM Eternal looks more fluid.
In 'slower' games like Battlefield 5, Witcher 3 or Deus Ex: MD I never noticed much difference. Overall, ever since screen tearing was fixed and G-Sync and Freesync came to the scene I haven't had any complaints about image quality in PC gaming in general.
Same goes for Xbox One X. With that machine though, the framerate doesn't hold up in all games. The latest Tomb Raider had gorgeous HDR effects but the framerate would occasionally tank.
Right now, I'm upgrading my PC first both for #WFH and because while it 'works' I can tell that my Intel 4th gen just isn't made with things like VR in mind and holds my RTX 2070 Super back. I could never get HDR to work on it either.
It held up extremely well for 6+ years though. Hopefully I can set-up my PC in a way that PC gaming on the TV is less of a hassle and otherwise I'll pick up a next gen gaming box next year when there's actual next gen games.