If Bend or Sucker Punch were on that banner as listed developers then people would know for sure that they were definitely showing something of their next games or at least assume that to be the case, it's not really a surprise that they'd be left off the list, even if it is pretty likely that both could be showing their new games.
With Santa Monica we know they're helping with things like Fat Princess Adventures, London have of course shown they're making demos and small things for VR.
Japan has The Last Guardian and Gravity Rush 2, either could get new footage, I suspect a release date announcement for TLG can't be far off.
IMO London are still Sony's 2nd biggest studio and for them to only have VR Demos and Singstar content in development, when they're a bigger studio than Guerrilla, Naughty Dog and only second in scale to Japan would be wasted resources if they weren't working on some AAA title or titles.
Personally I think Eight Days and The Getaway are still in development, with London Heist as their VR game, connected to The Getaway, but as a standalone release.
I think they could reintroduce either The Getaway or Eight Days at PSX.
Santa Monica has to be ready to show off something of a major title, obviously God of War is the one people know about and that has to have been in development for a few years by now.
Bend's game is confirmed as playable and running really well by Shu, same goes for Sucker Punch's 2nd PS4 exclusive, I wouldn't be shocked if both got announced at PSX, in a similar fashion to Horizon, with a good chunk of PS4 footage.
Sucker Punch's game has been in development for as long as Infamous Second Son was by the PS4 announcement, it's likely a new Infamous game considering ISS sold and reviewed well. I don't think Sony would cancel the series.
Bend were capable of making a similar scale of title to Guerrilla Cambridge, it's pretty likely they're a similar size of developer, so their big new game has to have a team of at least 70 people working on it (assuming they didn't go on a big hiring spree), for about 3 years at this point.
WB games are rumored to be working on a PS4 Superhero exclusive game, maybe a new Spiderman, Men In Black could get a video game reboot (with Sony owning the rights for that one).
Level 5 could finally show off their new game.
Not a new announcement, but Capcom could finally bring Deep Down back out, it's been ages since they showed anything new about it.
Maybe a couple of big 1st party things and a new 3rd party exclusive could happen.
Maybe a new Sly Cooper game could be announced to coincide with the movie release, though with Ratchet & Clank being Sony's big animated movie for next year maybe the Sly movie will be pushed into 2017 and Sony won't announce a new game until E3 2016, for a 2017 release.
Perhaps Rockstar could make a surprise visit and trot out Agent. ;)
Activision could announce they're collaborating on a new Crash game exclusive for PS4.
There's definitely a lot of potential at this event, obviously Sony already has a very packed out 2016 line-up, but some new gameplay of already announced games, new details and solid release dates would be cool.