User blog comment:Miskos3/Final Chapter in Official Color + Hiro Mashima's interview/@comment-200.8.22.175-20170728103827/@comment-2125188-20170801183058

Where did you hear that, cause that certainly isn't true. No mangaka would have anymore than 6 assistants. We've seen recent photos of Oda's workspace before, and the workstation for his assistants only has 6 work spaces. And Oda has said he averages about 4-5 assistants. Even if he have 10 assistants, he would still do the bulk of the work, cause like how in my last comment, usually the mangaka does all the character art (look how Mikeo Ikemoto and Yusuke Shirato couldn't draw the character's properly after being long time assistants) and important stuff, while the assistants do the less important things. If anything, having more assistants only takes the load off other assistants.

And as for Fairy Tail stuff, seeing as though the manga ending isn't stopping us from getting a 3rd season of the anime, I'd say it's safe to assume we will get some more fairy tail content for a while. I believe Mashima did quite a bit of stuff for Rave even after that ended, and was still working on some older stuff during Fairy Tail's first couple of years. So if that's any indication, a new work won't stop him from continuing to pump out fairy tail content. I actually wouldn't be surprised if Mashima's next work is pretty soon, and he does fairy tail stuff as well as his new series at the same time.