That would be a pretty far stretch. IMO
Between the fact our government has no idea how to control spending and the fact that there are about 500M guns in America; you wouldn't think it plausible to consider the left attempting to spend their way out of a "problem" by spending $200B to "confiscate" them? That's not that much money in the grand scheme of things.
It may not be a far and wide sweeping operation, but in small areas to dilute the concentration of firearms before any significant door-knocking occurs, I would consider it plausible. It could even be passed quietly for execution based on the money being used to "stimulate local economies."
That said, as many guns are made every day and put back into the system, I'd have to say that IF this were plausible, it'd have to be targeted towards unregistered firearms.
Then again...guns trade hands so often person to person, it'd be hard to stop that too, but I'm not sure if you can legally sell a firearm to an individuals without filing through your local FFL, like you can in Texas.
So...maybe it's just a California thing? They had a "sell your guns back, no questions asked" public affair a few years ago didn't they?