But all of the astronomy missions are (more or less) in earth orbit. The ones I work on, Planck and Herschel, will go to L2, which isn't orbit, but I doubt many bean counters will notice the difference.

This seems far too much like throwing the baby out with the bathwater. If NASA science is to become lunar and martian science only, I don't see any way the programme can be supported. I also don't see any way that international partners will support it since they're going to have other joint screwed over by this. It too a long time for ESA to trust NASA again after the whole CRAF/Cassini debacle. This could be that again multiplied several fold.