Probably going to catch on most with people who are learning supplementary skills. Most people who use Coursera, I believe, are men who already have bachelor's degrees. Maybe at first this will be the case with nanodegrees, especially since they are largely about computer science, as you point out.
In time, I think nanodegrees will be used for getting acquainted with introductory and fundamental skills and knowledge of a subject that's largely new to a student, but I don't know how claims of getting pretty large salaries will actually play out. I wouldn't expect anything extraordinary coming straight out of a nanodegree program. It will fit in somewhere in the hierarchy of higher education, not Ivy League at the top, nor something like hair salon school toward the other side of the spectrum. Its place will be closer to the top than the bottom, I think.