It's possible something else could replace those physics labs. Maybe Microsoft Research and similar non-academic labs will get larger, and expand out of computer science, more like the old Bell Labs? The U.S. could decide, alternately, that funding research is a priority, but doing it via hybrid educational/research institutions (the classic "research university") isn't going to work anymore, and choose to fund research-only institutions, e.g. bring the national labs back to the forefront. That's plausible, but I'm not sure there's political support for it.
My point is that with our current culture surrounding education, I don't believe that MOOCS will be powerful enough to topple academia. People just simply don't care enough about their education in America. I think that MOOCs would probably be much more effective in other countries, where education is not taken for granted.
However as time passes, and the culture around education shifts in the US, perhaps people would be more inclined to use MOOCS to their fullest potential.
> If MOOCs deliver on the promise of delivering more
> education to more people
It won't. It surely can make more education to be available to more people, but at the end there will be less people willing to use that oppurtunity.
Of course, if this comes to pass, then the same would be true for every country with ubiquitous access to the internet. In such a case, the proverbial rising tide would lift all boats equally :)