I watched the TV show, Future Weapons on the Military Channel last night and they featured two new bullets.
One was a .408 round for a new sniper rifle system. Very impressive; less recoil and a faster round than the .50.
The other was a 6mm rifle round for a new type of assault gun they were calling a 'personal defense weapon'. It is to replace the 9mm H&K, basically giving you the punch of a rifle in a sub-machine gun package.
Future Weapons : Military Channel