I'm suspecting if Demon's Souls does well, Sony might try to acquire them (if they haven't started the ball rolling already, and are waiting to reveal it). I've worked for studios that have been acquired before, and most of the time, these acquisitions don't just spring up out of nowhere, and have been in the works for quite a while before the news is made public. After re-reading the article about Bluepoint discussing how they remade Shadow of the Colossus, it didn't seem like they had an interest in developing their own IP, though they didn't dismiss the idea. Of course, their mystery remake that they said is the one they're the most proud of was Demon's Souls at the time.
If they stick with Sony, or become a PlayStation Studios development studio after DS releases, there are a lot of IPs they could potentially remaster. Even if we limit those IPs to third person action adventure games (which most of their remasters/remakes tend to be with a few exceptions), they still have a lot of options. Top of the list for me as far as dream remakes, in no particular order:
Jak & Daxter (the whole trilogy seems like a big ask, so lets just start with Jak & Daxter: The Precursor Legacy)
Alundra
Dark Cloud 1 and 2
inFAMOUS 1 and 2 (a full on Remake of those 2 would be amazing under Bluepoint)
Resistance Trilogy (such an underappreciated franchise)
Sly Cooper (a Remake that actually looks like the animated cutscenes would be so awesome)
Colony Wars
Warhawk
Legend of Legaia
I'd be up for any of these making a return on the PS5.
Dream 3rd party IPs if they stay independent, or perhaps Sony makes a deal with a third party to fund development on a PS5 Remake:
Metal Gear Solid 1
Silent Hill 1, 2, and 3 (proper Remakes/Remasters, not the shitshow Konami half-assed)
Legacy of Kain: Soul Reaver