No one can speculate on a "ban" that has not even been introduced to Congress yet. The President does not have a foot to stand on legally in regards to Executive Ordering gun control even though he still might try. I suggest reading Dianne Feinstein's gun control bill to see what some are proposing. Given the fact that Republicans control the House along with several pro-gun Democrats and Democrats wanting to be re-elected in 2014 I really do not see a whole lot getting done on "gun control" regardless of what the President and Vice President say. I think that it is really going to come down to if the Presiden wants to go against the Constitution of the United States to pursue this.
No good answers right now. I would suggest buying what you want to buy. The probablity of a retroactive, confiscation ban are slim to nill. If something is passed it will most like include grandfathering in items already legally owned.