do you think MA and others systems of self defense will have a big comeback %-}
I am inclined to doubt it. If anything, you may see a proliferation of knives.
Most people who purchase a gun specifically for self defense or home defense do so after something makes them feel a need to have the perception that they are protected. The whole point is to carry what they perceive as an equalizer that renders differences in strength and fighting prowess moot. Such people rarely put the time into learning the use of the weapon, and are thus unprepared to actually use it. But they
perceive that they are now safer. This perception is purchased and instantaneous. They now have a gun to flash at a bad guy with the assumption that the bad guy will be scared and break off the attack.
If guns were suddenly not available, knives would be the next choice. They're easily purchased and carried and seemingly simplistic to use. And it gives them something to flash at an assailant or tresspasser.
By contrast, people who take up a martial art generally do not do so out of an immediate need for self defense. Even rudimentary self defense skills take time to develop. If I am afraid that I will get mugged tomorrow, I will want something that works right away.
The only people who you would likely see take up martial arts as a result of a total ban on firearms are those who spend hours training to use their firearms and understand that the mere ownership of a weapon does not mean that one knows how to use it effectively. Of course many of these people will likely already know an unarmed MA of some sort.
Lastly, even if guns were completely outlawed, determined criminals will still obtain them, which puts the average person right back at square one: bad guys have guns so unarmed martial arts is no longer a perceived guarantee of safety. You might see a spike in the numbers of new students, but they will drop off quickly as they find out that MA is a fairly long road to anything resembling effective self defense against an armed assailant.
People in general, particularly in the US, are after a quick fix. Martial arts are not a quick fix.
Daniel