I hope Sony get most of their first and second party stuff updated at or near launch with Pro modes and that at least the third party big-hitters like CP2077, Alan Wake, Avatar etc see updates too.
Since Ratchet & Clank: Rift Apart was used to demonstrate the benefits of PSSR internally, I'd expect all Insomniac titles on the PS5 to receive Pro patches.
Guerrilla and some unknown partner are also expected to drop a Horizon: Zero Dawn remake somewhere around the launch of the PS5 Pro, so I'd guess they may want to revisit Forbidden West/Burning Shores and provide some light enhancements to those, bringing them on par with the remake.
Naughty Dog (The Last Of Us Part I, Part II Remastered, Legacy of Thieves Collection), Sucker Punch (Ghost of Tsushima Director's Cut) and Housemarque (Returnal) have all been known for updating their titles to take advantage of the latest PlayStation hardware in the past (The Last Of Us Remastered, Uncharted 4, Part II, inFAMOUS Second Son, First Light, Ghost of Tsushima, Resogun, Super Stardust Ultra), so I think it's likely that their PS5 stuff would get patched.
And it's kinda guaranteed that Arrowhead, Polyphony and Santa Monica are going to patch Helldivers II, Gran Turismo 7 and God of War: Ragnarök, since all three of those titles are and will continue to enjoy of long legs when it comes to sales, plus, the first two are actually live-service games.
The only one I'm not so sure its studio would actually care to revisit would be Demon's Souls, since Bluepoint doesn't seem to have a history of long-term support for their titles.
I expect there'll be another cut-off point after which all titles released must have a Pro mode. I recall the PS4 Pro having one (I think it was early in the following year, something like March-June...it was definitely mentioned in a DF article).
I think for the PS4 Pro the cut-off point was that all titles released in October 2016 and moving forward would have to support the console.