I'm betting that there's no way to get an AWB passed without some sort of "grandfather" clause permitting people to keep existing guns. I don't that even the Democrats, who are notoriously stupid in their lust for gun control, would risk an outright ban that involved confiscation.
Rather, I think it will be a three-step program:
1) A ban of future assault weapons/standard capacity magazines
2) Registration of existing assault weapons and a ban on possession of standard capacity magazines
3) Confiscation of existing assault weapons
Only #1 is do-able in today's political climate — and even that's not a slam-dunk. It will hinge on how much intelligence the Democrats can hang onto when they have total control. The Clinton AWB created such a backlash that it put the Republicans in control for a decade, A new AWB virtually guarantees a Republican renaissance in 2010 and sets up the 2012 Presidential elections. It's not impossible that Dems like Jim Webb and Ken Salazar move to head off an AWB...it depends on how strong the Blue Dog Dems' mojo is after the election.
I personally believe that an Obama White House will NOT be able to control its Socialists leanings and will go for an AWB very quickly. If cooler heads prevail, the AWB will come in the 2nd or 3rd year of the administration after they have their income redistribution plans up and running. If they administration garners high approval ratings and/or the 2010 elections retain strong Democratic control of Congress, look for a later AWB to include registration of existing guns as well.
I wish I was more optimistic.
Michael B