Roadracer, so far there has not been a cessation of the importation of 7.62×39. I don’t know if it will be a concern in the future, but there is plenty right now. The important thing to remember is that Russia is not the only one producing and exporting this ammo. Much of what we import also comes from the Ukraine, Germany, Taiwan, Serbia, and Romania, to mention a few.
As you mentioned, just about every manufacturer in the US now produces FMJ, HP, and SP 7.62×39. The guns and caliber are very popular so just the economic value of producing it will guarantee a good supply for quite some time. Of course, I can’t guarantee the price won’t change, but for the near future at least its ‘s still some of the cheapest ammo around.