I see the following possibilities:
1) The ban expires - Pre-ban owners lose money, but the ability to buy full-cap magazines at decent prices, and add evil features lessens the pain.
2) The ban is renewed - Pre-ban owners have a solid investment, but it will not appreciate much more from where it is, as it has reached full elasticity. Full-cap magazine owners have a great investment, that will probably rise over time.
3) The new ban is worse - It groups pre-ban and post-ban into a new category of completely banned weapons. Full-cap magazines are done, none to be made, none to be imported. No clones, nothing. The AR-15 is no longer made PERIOD. Pre-ban & post-ban owners have a great investment.
I think it is going to be 1 or 3, not 2. One side is going to have the votes to do what they want.