At the end of the day (figuratively speaking, literally it will be next spring), the question is what will people do if we are ruled against. Uncle says, "Then, giddy up." Armed Canadian says he would expect the NRA to engage in its biggest fund raising drive in history. Sebastian says it will motivate people in the short term and then the RKBA will gently fade away.
One alternative is a constitution convention as discussed in the comments to Kevin's post. Yeah, right. Our country completely and totally abandoned the enumerated powers model of the constitution during the Roosevelt administration. There wasn't enough outrage then to do a constitutional convention and the loss of just one amendment that is only exercised by something like 40% of the population won't meet the bar.
Going back to the revolutionary war we find that only about one third of the population were in favor of revolt against the tyrant King George. Another one third was opposed and one third were uncommitted. So, based on that model a case could be made that enough outraged gun owners might be able to pull off an illegal action of some sort.
I'd like to imagine there would be some sort Unintended Consequences revolt to the decision but from talking to many gun owners I know that won't happen. I know of three different FFL holders that were outspoken defenders of the RKBA and told of how if they ever gave up their FFL they would have a "mysterious fire" and all the 4473s would be tragically lost. When it came down to it, all of them turned them over to the ATF with only a mild whimper. Another person was exceedingly outspoken about how strongly they believed in their right to free speech and the RKBA. It wasn't even government action, merely pressure from potential investors and employers that convinced them to take their blog offline.
Several years ago one IPSC shooter I know was complaining about the stupid gun laws and how wrong they were. I asked, "So what will you do when your guns are declared illegal and you are told to turn them in? What will you do?" He gave me a confused look and said in a tone that indicated that he thought I was insane to even ask such a stupid question, "I'll turn them over. I'll complain, but I'll turn them over."
Who do you know that has actually followed through on some illegal activity in pursuit of securing liberty for future generations? Okay, if they are smart they won't tell anyone they broke law. So lets reword that a little bit; Who do you suspect may have broken the law in pursuit of securing liberty for future generations? I'll bet you can count them all on the fingers of one hand with several fingers left over.
Well, let's just say this, as to the first question "what will you do":
I will die before I will give up my guns; and I don't plan on dyin'
I figure, maybe 5% of gun owners HONESTLY feel the same way; and of those, maybe 5% will actually do something about it.
...250,000 is more than enough...
Even if I'm wrong by a factor of 10, 25,000 is more than enough.
Now, as to the second question, "how many people do you know or suspect have broken the law in pursuit of securing liberty":
Well Joe, it aint one hand, or two... let's just say that.