It'll be the same definition as it was while the same ban was in place 94-04. It wasn't a suprise, Obama said he was going to put the ban back in place during his campaign ("As President Obama indicated during the campaign, there are just a few gun-related changes that we would like to make, and among them would be to reinstitute the ban on the sale of assault weapons") During those ten years, everyone got to keep their rifles, shotguns, pistols etc. Its a ban on selling/buying them. Never said he was a champion of them, but he isn't going to pry all of someones guns from their cold dead hands like it was made out to be.

"there are just a few gun-related changes that we would like to make" And this was one of them. Guns aren't on the top of his list and won't be anytime soon with the economy, healthcare, Iraq, education etc in need of attention.