Something is coming, I think. Too much noise. That said, all they really can do is another capacity limit, maybe prohibit sales of new manufacture of say AR15's--and grandfather whatever is existing. And I think that will take a few months to pull off.
Not saying it isn't worth stocking up, but let's face it, 223/22LR/9mm ammo isn't likely to be banned. Get America to turn in anything? Yeah right. Stop the manufacture of new high capacity magazines, maybe a few select models? That did occur in the past, so, they could repeat that.
So I'd focus on buying magazines. Get that Glock you wanted, or at least the AR receiver. You can stock up on ammo later.