This is why if i were making an open source project, it will start off with GPLv3, with a commercial paid license if anyone wants to avoid the terms of the GPL. That gives the best of both worlds - open access to anyone, and if they want to modify, they must also be willing to contribute in some way.
And they better have that well documented. Legal might have something to say about it, for example.
It gives then a headache and it tells them you don't like what they did.
You have no obligation to continue hosting the MIT version, and you can release a new version of every commit under GPL.