My guess is Obama & Holder along with Feinstein will push for a total ban on mags with capacity > 10 rounds this time around. And I mean no grandfathering, etc. They will offer an amnesty period of several months to turn them in, and after that they will arrest anyone found to possess the mags. They won't search one's home for mags as a matter of course, but if there is a search warrant for something else, they will add hi-cap mag possession to whatever other charges they might have if they find them. And if melted mags are found following a fire or a LEO stumbles upon mags in the course of his normal duties, the owner will get the shaft.
For all practical purposes, possession at home will not cause any problems 99% of the time, but it would be risky to take them to the range, or out hunting. There would be no point in owning them other than in a home defense gun, but a quick change to 10 rounders would be necessary if you actually used the gun for protection. And God help you if a neighbor said he heard 20 rounds go off in quick succession.
This is worst case scenario.
Democrats have been waiting patiently since 2004 for an event to provide impetus for a new ban, and now they have it. It was a matter of time.
When the time comes, be ready to crucify any Republicans that stands with the Democrats. They have to understand fully that siding with any new gun control will result in political suicide. Instant death, no quarter.