Re: Inhumans in development?
I don't see how the Inhumans are connected to the X-Men more so than the Avengers. They don't have much to do with either one equally. If anything they're more connected to the Avengers because of Quicksilver and Crystal's history (which of course they may never use but w/e).
And the Kree should be the villains of the film, which as Mondragon pointed out can connect the Inhumans to several franchises in itself, including potentially the Avengers if they use the Kree in the third film.