I think it's pretty clear at this point that everything Sony's working on is bound for the inevitable PS5, but for some reason they don't want to show it yet. They've also been increasingly reluctant to do E3 shows for the last few years as they've slowly run out of "big" games to show. Remember last year when the story going around for a long time was that Sony wasn't going to do an E3 show, but instead something akin to a Treehouse Live with the 4 games they had to show? Then suddenly they had an E3 show pull together at the last minute, which showed in how all that played out.
I think Sony's been wanting to step away from E3 for a while now and the lack of PS4 games to show (especially from 3rd parties) pretty much forced their hand here.