White Knight Chronicles remake with full trilogy and story/MP
Killzone 2
Allundra
Resistence Trilogy with MP from 1/2, (kill 3's MP with fire)
Summoner remaster
Metal Gear Solid or Silent Hill would be my top picks, though I wouldn't say no to a full modern remake (with substantial QOL improvements) for GTA 3/San Andreas, Shenmue, or Twisted Metal
As much as I'd like to see MGS4 freed from the PS3, I really think the deserve to do their own thing. Their technology is incredible and they've sunk their teeth into the inner workings of some of the best games ever made. I want to see what they can do.
Assuming Demon's is a critical and/or commercial success, there is zero doubt in my mind (literally zero) that their next project will be Demon's 2, Bloodborne Remake, or Bloodborne 2. Also Sony will probably buy them.
Honestly? They've proven themselves time and time again to be a great studio so I think Sony should just buy them up and let them work on a new IP for them. They're nearly 100 people now so it wouldn't take many more to upscale them into a 'proper' Playstation Studios team.
If they had to make another remaster though I'd love to see something like Syphon Filter. I appreciate it'd be yet another Sony 3rd person action title but with the MGS series on indefinite hiatus and no sign of further Splinter Cell titles I think there's a strong market for that kind of military based action adventure.
A remake of any notable Konami 3D game, Parasite Eve, Vagrant Story or any other legendary videogame I haven't played for age reasons.
I would like one day to play a remake of Ultima IV, since it's seemingly an incredible masterpiece that was way ahead of its time, but I doubt they would be the best choice to remake it