I honestly don't think the long take is dead. I don't think it'll die any time soon either. After all, in my opinion, it is one of the most interesting types of takes. I admit that I like the apparent chaos of montage, with its the juxtaposition of conflicting images, but sometimes I like long takes because they give you this weird false sense of security. I think it is because when you are watching long takes you get immersed into the movie, with this false feeling that what we are watching might be real, although in the back of your mind you know its not. Long takes make you feel as if you were watching something actually go on, the framing of the scene being the limits of what you can watch, just as a voyeur looking into a peep show. I don't think that long takes make the viewing experience any more "real" than any other take, but it does make you more aware of your limitations as a viewer (which in its own way, might be more real).
When we are watching a film with very little cuts, the first thing I notice is how elaborate the planning of that scene must have been. After all, one mistake means much more in long takes than short takes. I don't know if this works with everyone, but I become more aware of cuts and takes in long takes than in the typical short take scene. I think it is because it just appears so much more work to coordinate everything and so much more rare to see the same scene in different angles. I just become so much more aware of pans and zooms, and everything has to be so smooth and pretty for it to work... It is definitely a calmer kind of take than montage, and I think that depending on the purpose of the film, the long take would work perfectly in enhancing a kind of feeling or emotion.