There may be some isolated instances of violence. But I really doubt the average American gun owner would care enough about this to risk their comfy existence, not to mention their life. We as a nation are way too soft. We did nothing in 1994 when they banned scary-looking guns, for example.
I think the more likely scenario if the USSC rules no individual right is a push for a constitutional amendment to "clarify" the 2nd for those too stupid to understand plain English. Not to say it would pass.
Perhaps you did nothing. I did what I thought was necessary. It didn't involve killing anybody. I own many arms similar to those banned, but just as effective, that I wouldn't have owned otherwise. The well-regulated militia is just a little better off for it.