Then they will complicate the process to the point it will be near impossible to comply without risking a federal felony.
They will do it is small baby steps A.K.A. the Overton Window approach...
In fact I think such an operation has been in effect for several years.
I think you're right; I believe they've been doing this constantly.
(Sandy Hook may've been a test-operation to see if they'd "moved the window" enough.)
Then they will complicate the process to the point it will be near impossible to comply without risking a federal felony.
It already is. See Three Felonies a Day.
My guess is they will eventually stop with trying to outlaw guns and use the Obamacare model instead and use taxes and loads of red tape to put gun ownership out of reach just like the already did with automatic weapons.
That's my supposition, too.
They can set it up as a "technical violation"/amnesty contract type deal wherein you are effectively admitting guilt and waiving the right to jury-trial.
Given the general acceptance of denying felons rights, they probably won't get a lot of blow back if the pick up a few "technical-felons" at a time.