Deformable geometry for enviroments outside of foliage isnt a big deal for 99% of games made. As far a characters go they wont be able to reap the benefits of nanite outside of armor, gadgets, accessories, weapons etc..
They also added foilage support in most recent update. There are animation limitations on the foilage but im sure they will find work arounds. Event tbougj its working.
12 years ago Carmack was all about researching virtualized geometry solutions using SVO techniques and most other industy leaders werent very optimisitic about the progress including eventually Carmack himself which quickly abandoned the tech for awhile. Since then outside of that austrailian company most people werent even discussing it anymore. Epic kept R&D8ng it in secret and didnt reveal that fact untill 2020 catching most studios completely off guard. Considering how much printed money Epic has made from Fortnite over the last number of years and how much they have had to spend on what seems to be a very robust R&D team and fact they have already been working on this nearing 10 years leads me to be very skepticle about how fast the dev darlings around here can respond. I just dont think Spiderman 2 is gonna have some impressive use of virtualized geometry but I fully espect to be gaslit here left and right about its "technical" merits as it pertains to an "next gen" exclusive.
On another note: I think the best use case for Nanite characters is Robots with an industrial design aesthetic....think Armored Core.
You forgot the part where Epic were "caught by surprise" by Sony SSD I/O for PS5 and had to rewrite their I/O pipeline in UE5 to support it.
Also I think you're underestimating how much platform holders (particularly Sony & Microsoft) keep in touch with companies like Epic. Whatever stuff Epic were R&D'ing for UE5 over the years, I'm sure a couple of their folks were sharing insights, maybe even demonstrations, to people at Sony, Microsoft, AMD, Nvidia. People in this industry tend to talk somewhat with peers at other companies, especially in the case of platform holders with 3P devs & pubs.
So I don't think Epic caught anyone off guard with UE5 and if anything, Sony caught them off-guard with how feature-packed PS5's SSD I/O subsystem was, to the point Epic had to rewrite theirs. But systems like PS5 & Xbox Series were always going to be prepared for UE5, just like how PS4 & XBO were able to run UE4. Why would it be otherwise?
Lastly you're underestimating Insomniac's skills and talent. I don't know what engine they use specifically, but they already have one of the best-looking games of the gen so far in Rift Apart, and they're absolutely going to push past that with Spiderman 2. I think you're going to be quite surprised with what stuff Spiderman 2 is pushing on the technical side; Sony are definitely going to invest heavily into a big marquee release to, among other things, be a showcase of what the PS5 can do.
There are a number of demo's showing performance with and without mesh shders gives a boost of between 500-1800%.
I understand that's game dependent, but they are leaving alot of untapped potential on the table.
TBF those are very limited demos that are doing nothing other than generating polygonal data. There's very little (if any) game logic, physics, AI etc. running on those.