After Heller was argued and won, the Dems don't have a leg to stand on, and they know it.
You're making the assumption that the Legislature ponders the Constitutionality of the laws they debate (they don't) and making the mistake that they read, understood, and give a rats behind what's in Heller (they didn't, can't, and don't, respectively).
Heller won't affect the actions of the Legislature at all. They'll continue on their merry way however they see fit. I don't think they'll do anything as stupid as enact another AWB, but if they did Heller isn't much of a comfort either.
It took 32 years to get DC's handgun law overturned. Chicago's is still on the books but being challenged. The courts move slow and going from a .38SPL revolver in Heller to an AR-15 in another AWB is a big leap, and I'm not sure the courts are going to side with us that quick on the issue. Well, aside from Scalia. :)