The mutants are not being moved to a universe of their own, nor are they being turned into inhumans, nor is the mouse going to outright kill a product that is still profitable. The mutants are, however, occupying a position in the Marvel comic universe which could be more profitable for the mouse if only it were occupied by another property for which said rodent held the full movie rights.
Enter "Secret Wars", a story closely associated with these words:
What do the X-Men dream about? A world where humans and mutants coexist peacefully, where mutants are no longer persecuted for being born different. At the end of Secret Wars, they just might get what they wished for - living in a world where mutants are no longer hated and feared. With that role no longer occupied, it will soon find itself taken over by the inhumans and the X-Men will find themselves in a position they have never been before.Originally Posted by The Beyonder
Consider the words of Alonso from the interview Alonso teases "new world" for X-Men following "Secret Wars":
The mouse will not kill the body, but it might rip out the soul under the guise of a happy ending.Originally Posted by Alonso