Ammo has pretty much reached its full potential. Firearms are pretty much at their full potential. I certainly can't see the next step in firearms or ammo development. The Super Short mags were an attempt in both areas that didn't amount to much. Plus, there is still the laws of physics that control recoil and that may be the next thing to be got around.
New alloys may make guns lighter, and perhaps new formulas will make cartridges more efficient, but not by leaps and bounds.
