At this point, Takaya should come out and tell the fans if he's done, rather than leave the series on permanent hiatus. If he's keeping the door open for a return, he should also make it known. George R.R. Martin gives status updates now and again, even if no one expects him to realistically finish the books. Instead, Guyver fans have been left in limbo.
Takaya is the wrong side of 60, and we saw with Kentaro Miura that anything can happen, but at least Miura was still working on Berserk when he passed away.
I have to wonder if Kadokawa won't officially end the manga, as they still need the IP to hawk figurines and merchandise.