I predict end of 2014.
Obama will stage an(other) incident and they will say they tried but it is just too dangerous to the public to allow the grandfathered firearms to remain. They will give us 120 day to voluntarily turn in or dispose of our firearms. That will get around 90%. Then they will try to come get the rest. That will get another 7-8%. Then they will have a 30 day general amnesty. That will get another % or so. They will then WACO the rest.
No, you are way too pessimistic. First, they have to get gun registration through the House, and that ain't going to happen before 2015, at the earliest.
If they ever pass that, there will be widespread civil disobedience on actual registration, and the program will be a failure like it has been in Canada. As far as any eventual collection goes, they will have to buy back the guns turned in and the cost of that will be too large to get through Congress, who will prefer to spend the money on Boomer healthcare and SS.