I've encouraged my brother (RPAL holder, no restricteds, yet) to purchase a stripped AR15 lower, as well as an inexpensive pistol (Tokarev), for exactly this reason.
I think (and I could be wrong), this would "grandfather" him into both the restricted long gun and restricted handgun categories, should it come to that.
Yes, there are flaws in my line of thought: outright confiscation, possession only/no further acquisition allowed, or even a division of restricted long guns and handguns by calibre/gauge, type of action, etc.
I'm still hopeful it won't come to that, but just in case. Or in case Justin.
Call me crazy, but a $400 "insurance policy" by purchasing these two items seems like smart move...