I think Sony only pulled out of E3 this year because they won't have much new to announce for the PS4. E3 isn't cheap and requires a lot of planning. Sony probably determined that the costs outweighed the benefits this year and decided it was better to not go. We've probably already seen every major PS4 exclusive to release this generation. Days Gone should be out before E3 2019, which would only leave The Last of Us Part II, Death Stranding, and Ghost of Tsushima. We've also seen a decent amount of footage from each of those games and all that's left is to announce release dates. With God of War, Spider-Man, and Days Gone all having their release dates all announced on the Playstation Blog, they'll probably do the same for the remaining three exclusives.
I expect they'll be back at E3 in 2020 once the PS5 has been officially revealed at PSX 2019.







