I think it would be stupid for them to try to ban firearms entirely.
#1 - They won't get them all, if they even get most. Just because someone has a CCL doesn't mean they own a firearm. I'd love to see them try to prove it. ;)
#2 - I'm sure a lot of people in some states would be more likely to revolt than give them up. This could be the straw that breaks the camel's back.