Won't happen.
First, let's say an anti-gun government swings into power in 2008 or beyond. One definite action will be to prohibit the importation or sale of any more parts kits, barrels, magazines or semi-auto weapons, period. They will say "Hey, your currently legally-owned weapons are still yours, so we aren't really infringing your rights." What are now post-ban weapons will become the new pre-bans. Step one.
Now the anti's need to wait and let the numbness set it. Wait until the outrage cools and attention is focused elsewhere. Wait for an event...a terrible event involving a shooting, preferably using an "assault weapon". They'll get one eventually or make one up.
Suddenly the cry goes out to "do something" about the "flood of weapons on our streets". Never mind that 100 million legal arms were NOT involved in the shooting, one of them was, and that's enough. Step 2 will demand national registration of weapons as a "common sense measure to help law enforcement" find the criminals. You can keep them for now, Mr and Mrs America, just register them or go to prison.
Now of course there will be massive noncompliance, but guess what? Say you refuse to register. Can you go out to the range now and shoot them? No. You are now felons, past the "amnesty" and you can do nothing more than clean and admire them with the curtains closed. You can't sell or trade them either...they're now contraband. But at least the gun grabbers can't come in and get them, right?
Maybe not just yet. There's still one more powerful trick up their sleeve: ammunition. "Common sense" dictates that anyone who orders 1000 rounds of .223 should be checked against a list of legal registered gun owners. Say, here's someone who ordered some ammo...and an AR-15 scope mount...and he's not on the list of AR-15 owners. Hmm.
So they don't have to break our doors down to drown us slowly. THAT is why we must resist now, resist what are pandered as reasonable or common sense measures to back us into a corner. As for all the "sporting" gun owners that see no problem in outlawing "assault weapons", how long do you think the gun grabbers will wait before dropping the bombshell that your scoped 30-06 or pump 12-gauge is actually more powerful and devastating than an AK-47? Soccer moms will be surprised and shocked. Add the constant PR pressure of anti-hunting, animal rights, demonizing the image of evil gunowners and "save the children" and there you have it, game, set and match.
Will we see an actual civil war over this and other values? I doubt it. But some people sure as hell will have to make the ultimate sacrifice to make them back off and think, "is this worth it?".