First, just wanna say I've got mad respect for you (and @Rexy as well) for holding the torch all those years, providing a training ground that fostered musicianship and helped so many of us develop their skills through friendly competition, all the while paying tribute to lesser known game music, which is a mission we have in common. Every time I fell off the llifeboat and tried to claw my way back into remixing, this compo was always there to help me find the north again. So believe me, I do not wish to see it gone anytime soon.
As for promotion, while I'm nowhere near popular or prolific enough to be giving PRC the props it deserves, I'm willing to do what I can on social media. You could also get in touch with starla for advice, because the OHC has got a thriving community and overwhelming participation every week, so she's bound to know the magic formula. Lastly, I believe community Discord servers (OCR, ThaSauce) would be a great place to advertise the beginning of each round, cause I betcha a lot of new remixers bypass the forums to go there.
In all fairness you can't be expected to keep the compo alive all by yourself. That's admirable, but also defeats the whole purpose of a 'community' event.