Think about possibilities.
Imagine what can happen 10 years from now, when Udacity covers the whole curriculum of all major majors, not the few courses that they managed to build in few months of their existence so far.
Imagine what happens if they have 10 years to tweak and improve their lectures, based on feedback on data they gather from past students. They can only get better! (which is not the case in physical universities, due to rotation of lecturers and the fact that some of them were never good to begin with).
Imagine that they hire faculty to start doing real research project, the way MIT, Standford et al do, all coordinated via internet, live video calls etc. Imagine they do it so well that they are allowed to start giving Ph.D.s.
Imagine that they start giving master degrees via testing centers, after you pay a modest fee for taking the test (something they have already started doing).
Imagine that they start coordinating in-person study groups via meetup or some other such service, the way e.g. programmers self-organize and create "Android SF user group" and such.
Those are just 5 minutes ideas that I'm sure are not escaping Thrun - he's much smarter than I am.
The disruption here is zero cost. If they can maintain that and expand to offer more, better courses, it'll be massive.