The problem is that digital came to be not because of the quality or anything that has to do with the movie goer but because it is much cheaper and much more convenient for studios. Now studios do not have to worry about printing film and deciding how much film to print.
They do not have to get into situations where a bunch of theatres showing a high budget movie stay empty and a hot selling small movie keeps selling out tickets, but they cannot open new theaters for the small movie because they did not know it would be so hot and did not print enough film copies for it.
Now they can open as many theaters as they want for the hot movies, thus immediately satisfy demand without rushing to print new copies, waiting for the new copies, etc.
So yes, digital is here to stay. Not because it looks better (it mostly doesn't), but because it is more convenient for studios and theaters.
And if 3D does not work, the movie theaters will probably crank up the resolution again but they will keep it digital.