My guess is another remaster/remake from Bluepoint Games, they've been quiet for a while
This is probably what I'm most excited about, though not sure it will be part of the next SOP. They did tease a few months ago that they were working on another game that many would be excited for and that it was on par or larger in scale than SOTC, so it has to be a decent sized game. The only ones I can think of, if Sony related, would be:
Personally, I think either of the last four would excite me the most. And while they aren't the largest of Sony's IPs, I would love remakes of Drakan and/or Ghosthunter. Those games deserve some love. At least as PS2 on PS4 releases.