I don't see it happening. There's no logical reason for it, but I'm not sure SCOTUS would toss 922o, because even Scalia seemed to use the "in common use" argument in Heller- thanks to the NFA (nothing NFA regulates is commonly used) and the Hughes Amendment, full autos aren't in common use. The angle of the amendment being illegally added on to FOPA as a poison pill and getting tossed by the courts is an interesting one, but I have a feeling the courts would just say "It's been this way for 25 years, it sucks, but we aren't going to do anything about it" rather than potentially open other laws to this kind of scrutiny (where opponents sue over the legality of passage of a law they don't like).
IMO, the only way it will be repealed is legislatively, which means tacking it on to another "must pass" bill, but even that requires some assistance from the party at large- something we won't get. While pro-gun forces have done well on state and local levels, we've largely been shut out on the federal level- the most we can point to as a victory is a lack of action- the sunset of the AWB provision of the 1994 Crime Bill. Carry in national parks might show a bit of motion back to our side federally, but that was an extremely small step.
Self defense gun enthusiasts are still seen by many as the "crazy uncle" of the RKBA community. NFA enthusiasts doubly so. Until that changes, we won't see much movement.