Looking for whatever information I could find, it seems this likely isn't a case of the manga getting axed, so much as it is the artist suffering health issues. And considering that it'd take one-and-a-half times again as much as has already been released just to get to the point where all the sages are gathered (so, another 15 years worth of serialisation), I can empathise with them.
Still, in the tweet announcing the final volume, the artist used the words 一旦の区切り, which I'm struggling to read as anything other than "temporary break/milestone", which I'd interpret as, the series might get picked up by another artist. Though I guess that might just be a reference to the series continuing in the form of the light novel. Edit: Thinking more about it, it was probably just a "soft" way of phrasing things, as is so common with Japanese.