308, the creedmores, especially the 6,5, 22 lr, maybe the prcs, let's see. Maybe the 300 win mag too. Of the european ones the 7x64 and the 9,3 x62 will likely also stay popular.
That is what i think might stay popular and easyishly gettable in shops. As some has already mentioned, if the market was rationality driven, a lot of the old european cartridges, made for long for caliber bullets with long throats and pretty low twist rates barrels, like the 6.5x 55 or 57 and the 7x57 should also really fit the non lead era well, but i just doubt they'll become popular. Let's see if there isnt soon a 7 mm creedmore, to try and kill of the 7mm08 and 7x57.