Well Quantic Dream haven't announced their game yet.
London Studio haven't released a new big AAA game since The Getaway on PS2, that was 2004, they're the second biggest 1st party studio at Worldwide Studios, only Japan is bigger, so they could definitely have a bunch of things that have been in development for years.
The Getaway & Eight Days were never officially canceled once and for all, rather they were put on hold back in 2011, maybe they both got moved to PS4 at around the same time The Last Guardian did and they could be ready to show on PS4.
I suspect we'll see at least one proper VR game from London at some point or maybe some new experience could be shown for VR.
Gran Turismo 7 has to be shown at some point and GT is huge in Europe and the game is meant to release before 2017.
Bend's game could be ready to show here, same goes for God of War on PS4 and any amount of 2nd or 3rd party exclusive deals could have been worked out.
Evolution Studios may have shrunk down to Media Molecule levels of size, but that doesn't stop MM from working on multiple projects.
North West were recently announced as a new VR 1st party studio, maybe they will show off something.
Pixel Opus hasn't announced anything since Entwined, they could be ready to show their next project.
I think Sony definitely has the content to deliver across their future conferences, it all just depends on how long things are along in development and where it fits into Sony's marketing plans.
The potential is certainly there for yet another big event, we'll see what happens on the 27th, I doubt they'd be holding an event if they had nothing decent to show.
Personally I'll be happy to see new stuff for Dreams, maybe new footage for Horizon, RIGS and their smaller PS4 exclusives. New games are always welcome.
