It's the 6.5 mm Grendel, and I've been following its development a bit, since I'm an amateur shooting and reloading enthusiast. It looks like an ideal compromise between power and size. It's based on the 6 mm PPC, which is a champion's target round. With low-drag bullets, it's supposedly capable of 1000 ft-lbs of energy out to 1000 yards. 1000 ft-lbs is generally considered to be the energy required for efficient kills on deer, which happen to be human-sized. I imagine it is a lot more efficient than the .223 in short barrels, too, since it is a shorter, fatter cartridge.
From a web site on the subject, http://www.competitionshooting.com/pages/708565/:
"The 6.5 PPC is able to equal or exceed the ballistic performance of the 7.62 NATO / .308 in terms of retained velocity, trajectory and wind deflection while operating with 50% less recoil. (6.5 PPC 123 grain @ 2750 fps = 7 lbs vs. 7.62 NATO 185 grain @ 2500 fps = 14 lbs: Reference- 5.56 NATO 77 grain @ 2850 fps = 4 lbs) ".
It will be interesting to see where they go with this. A relatively small increase in weight gives a very large increase in power over the .223 with this cartridge.
The idea for a cartridge like this (the 6.5 Grendel) occurred to me independently years ago, but I didn't have the wherewithal to produce one...I've been wondering for a long time when such a cartridge would evolve.