The problem of sculpting an Assault Weapons ban is tough for lawmakers. It took two tries in California and it is still beatable. Most AW's come in a CA legal version. Here is how CA did the laws.
The first law named off all the guns that looked like an AK, an AR, an FN-FAL or others that looked menacing. That did not get them all as other un-named manufactures started making them.
The second law took a stab at outlawing them by description but savvy people figured out how to get around that too, hence the CA legal version(and apparently Connecticut legal, based on the news of the school shooting) by those not named in the first law.
The limits in CA include no flash hider, no removal mags (more on that), and a max count of features like pistol grips. It takes a flow chart to design the gun but it is legal if you can. Also you can not buy mags with a capacity of more than 10 rounds in any gun but it is not illegal to posses them (as it apparently is in Washington DC as that news correspondent found out the hard way).
CA AW owners get past the no removable magazine with a "bullet button". The mag release will not work except by using a tool to remove the mag. The nose of a bullet is a legal tool (tested in court!) so to drop the mag you just press the button with the point of a bullet or any tool. One manufacturer even made the mag hole in the AR lower blind, and riveted in a 10 round mag made from a 20 rounder. You loaded it by breaking open the gun to reveal the top of the mag and either loaded the mag one at a time or used a provided stripper clip. They stopped making that lower when the bullet button was introduced and became popular.
Any 22 is exempt and the ban applies only to semi-auto center fire magazine feed rifles and some hand guns (like an UZI).
So even if we get a AW ban there can be a bunch of loop holes that may take some time to figure out and legal action to get around. I highly doubt they would try to ban all semi-autos as that would include a 120 years of guns. The constitution requires compensation for any property the government takes by legal action. Getting all 300 million guns at market value would break their budget all the more than it already is so they probably won't try that.
The left keeps saying the NRA is crippled but I certainly don't think so. They offered a solution of armed guards at every school and the stupid left has claimed we can't afford that. But the counter to that argument is "How much do you care for the children of America?", which is a compelling argument. The left position is flawed and it is so obvious that all they want is an in to gun control and don't care about fixing the problem. The real answer is looser laws on committing the dangerous and insane and guarding our schools with trained security. But any home or school or mall or whatever, where guns are forbidden, is a ripe target for these insane shooters. Keeping security guns out of schools makes them a prime target and it is obvious.