The alternative is revolution, and they have the army.
The Army is weak and stressed at this point. They're attempting to prepare for this scenario, but in reality it will mostly be foreign troops and/or private security firms called in to do the dirty work. They won't feel bad about shooting at us.
But remember there's 80 million gun owners in this country. They know if only 10% felt like participating it would be over in 24 hours. This has probably been the ONLY thing keeping us safe from hardcore tyranny the past 25 years. They have to settle on gradually increasing their power over a long period of time, forcing us to psychologically accept our servitude and relinquish our arms willingly.