I think this argument needs to be parsed a bit. Regarding the actual RKBA as an actual established Right even before the Constitution we need only look at Heller.

This meaning is strongly confirmed by the historical background of the Second Amendment.We look to this because it has always been widely under­stood that the Second Amendment, like the First and Fourth Amendments, codified a pre-existing right. The very text of the Second Amendment implicitly recognizes the pre-existence of the right and declares only that it “shall not be infringed.” As we said in United States v. Cruikshank, 92 U. S. 542, 553 (1876), “[t]his is not a right granted by the Constitution. Neither is it in any manner dependent upon that instrument for its existence.

So with that out of the way the only option to simply render that moot is Constitutional amendment and for the foreseeable future that looks extremely unlikely. The much more likely approach would be to push whatever restrictive laws believed to be able to pass legal scrutiny. Outside all the national level screeching the real crunch will be in the States. Multiple states have various degrees of "assault weapons" bans already on the books including CA, CT, HI, MD, MA, NJ & NY. Variations of these laws can spread, become even more restrictive or both. More restrictive, at some time or another assuming that ball really got rolling, could include not only all semi-auto rifles but pistols as well.

At some point the onus is going to fall on SCOTUS which will make for an enormous decision. Heller clearly states what has been seen as being "protected" are those weapons "in common use at the time". There are lots and LOTS of semi-auto rifles, pistols and shotguns out there. To call such weapons "common" would be a vast understatement. This will then run directly into this: (also from Heller)

Thus, any attempt in theory to apply strict scru-tiny to gun regulations will in practice turn into an inter-est-balancing inquiry, with the interests protected by the Second Amendment on one side and the governmental public-safety concerns on the other, the only question being whether the regulation at issue impermissibly bur-dens the former in the course of advancing the latter.

The 2A in and of itself seems to be on pretty solid ground. What becomes of it from a regulatory standpoint is much more up in the air going forward.

If there's one thing I've become certain of it's that there's too much certainty in the world.