In theory - yes, nothing prevents Sony from going to E3 2019 with Death Stranding/TLOU2/Ghost of Tsushima again, add a splattering of smaller first-party announcements ( we've heard there are still unannounced PS4 games, etc etc ) coupled with third-party game announcements to pad out a conference.
But from an optics and perception perspective? Sony managed to slog through E3 2018 without any new game announcements, but thinking that they can just 'do it again' for E3 2019, even if they have significantly more third-party games there is naive.
To host a major E3 showcase comes with an expectation that you will be bringing the big-guns and even though Sony's big 3 games are big-guns, they've exhausted the 'gameplay reveal' card already. Even if the quality of the trailers and showcases that is possible from those 3 games are better this year, it's no longer as sexy or appealing from a press conference perspective.