I don't know about that, I can see your point about it possibly being a "fad" and certainly there is a circular nature to these things, but I know the directors themselves love a chance to tell longer, deeper stories, and theres been a lot of success, arguably more than failure.
Theres a feeling thats been stated many times by them that Hollywood movies are dumbing their work down, and that TV allows them to do what they want better. Also aren't cinema attendances generally falling, while consumption of TV, and online delivery, rising?