At the time "Well, Sony doesn't have anything much to show" was the given excuse for the end of PSX and the underwhelming E3 2018 showing. I'm not sure how much that really flies anymore, given that they could have saved up announcements for a theoretical PSX 2019 that featured TLOU2, Ghosts of Tsushima, and Dreams.....but they chose not to do so. Instead they did a huge TLOU2 media blowout less than 8 weeks before a PSX would have happened. It seems pretty clear that they would rather reveal things throughout the year on their own timetable rather than having to save big news for a particular date that is set in stone.
We're now on the eve of a console launch, and Sony most certainly does have things to show.......yet they're still not showing up to E3. If E3, GDC, PAX, and Paris Games Week aren't worth their time and effort then I doubt they're exactly itching to throw another PSX (for which they would have to pay entirely out of pocket, instead of just buying booth space).
Is PSX dead? Is PSX "on hold"? Seems like mostly semantic argument at this point. I would be pretty surprised if they do one in 2020......especially now that the TGAs are well-established, and they can just piggyback onto it for any big December announcements.