It has been said the Inhumans movie will eventually be cancelled which is a result of the fallout between Marvel Studios president Kevin Feige and eccentric billionaire Marvel CEO Ike Perlmutter.
"I think Inhumans will happen for sure. I don’t know when," Feige said. "I think it’s happening on television. And I think as we get into Phase 4 as I’ve always said, it could happen as a movie. I think it would be super cool."
Note: Feige doesn't specifically state the Inhumans movie WILL happen, just that he thinks it may or that it could.
Regarding the Inhumans rumor, it was more or less said Marvel would eventually state the reason for the movie not happening was due to the creative process or not being able to find the right director, etc, and not the real reason being Kevin Feige having booted Perlmutter and his Marvel Comics people from being involved in the movies.
Perlmutter is said to be responsible for green lighting the Inhumans movie in the first place, and Perlmutter is also responsible for Marvel TV and Agents of SHIELD which features the Inhumans (and also the reason why Marvel TV and the Marvel movies don't crossover or get along).
It's possible that if Kevin Feige does move forward with an Inhumans movie, that it will be set far enough in time away from Agents Of SHIELD's less than stellar performance of the characters, and the Inhumans movie will also feature the characters not on the TV series with Black Bolt, Medusa, Karnak, etc. (and also probably not Bendis' Quake as Bendis is a part of the booted Marvel Comics committee).
Vin Diesel also previously hinted he may be playing Black Bolt in the Inhumans movie.