I'm not too worried about it. Folks in the know have said E3 has consistently gone up in price, which even for companies like Sony has a limit.
It is more of a detriment to E3 than against Shenmue III. It could still be there, as Deep Silver is with THQ Nordic and they have become quite a prominent company of late with developer acquisitions.
Insiders on Reddit that seem fairly knowledgable have hinted Sony will have their own conferences, most likely for PS5 stuff, which is sooner than folks seem to believe.
And let's go ahead and call the hand as it is, honestly---Shenmue has it's following, a massive one that resurrected it. It may grow slightly due to Shenmue I and II being available again, but no amount of marketing is really going to shove it into the "mainstream" territory.
It is and always will be a niche title, though it's popularity may grow to be similar to the Yakuza series, but not much more than that.
I would like to edit in an addendum here--with the recent leaks suggesting conferences of Sony's own to usher in, presumably, the final swan songs for PS4 and ramp up the hype and reveal of the PS5, I would not be surprised to see Shenmue at one of these conferences as a "swan song" title.