Officially announced games:

The below games were explicitly confirmed by Sony in a recent interview.

Days Gone
God of War
Uncharted: The Lost Legacy
Spider-Man
Gran Turismo Sport

Sony promises "some big announcements" regarding Japanese games. They didn't necessarily say they were exclusive, but they were clear they were console games.

Maybe, maybe not games:

Detroit: Become Human I had in presumed games before, but Sony didn't list it explicitly when they talked about what they were showing.

Horizon DLC: Sony has said there's Horizon DLC coming.

Knack 2: Sony has been known to leave their smaller games out of their E3 press conferences on occasion.

Everybody's Golf: See Knack 2.

Matterfall by Housemarque: See Knack 2.

Dreams: It's still not clear when or if this is releasing.

The Last of Us 2: This strikes me as a 2019 title, so it's probably a bit early, but they did announce it super early anyway.

In theory, Michel Ancel's Wild is still a thing.

Rumored games:

Sony has a new quiz party game called "That's You". You use your phone (and phone camera) in combination with the game. It focuses around doing things with your face and appearance, hence the name.

Additional notes:

Sucker Punch hasn't announced a game in a long time.

Sony has a VR headset that they might announce games for.

Sony has a portable system that hasn't 100% officially been killed yet, but don't hold your breath.

Sony has marketing partnership with Destiny 2, Call of Duty: World War 2, Star Wars: Battlefront 2, Far Cry 5, Marvel vs. Capcom: Infinite, and FIFA Soccer 18, and they usually have one with NBA 2K, so any of those could presumably show up on stage.

Take-Two has said that Red Dead Redemption 2 won't be at E3, so don't expect that one despite the marketing deal.

It's always hard to predict what Japanese publishers and developers will do, along with their odds of inclusion in Sony's E3 show, given this has changed dramatically on a year to year basis. The same is true of indie games.