Surefire is apparently now pimping a quad-column magazine for the AR platform.
The four-column magazine is not really anything new, of course. I had a SITES Spectre pistol back in the mid-'90s that ate out of 30- or 50-round sticks, and the concept's use in modern firearms apparently runs back at least to the Finns and Argentinians in the 1930s.
The metallic cartridge firearm is really very mature technology, and there is very little new under the sun.
The Boberg XR-9's feed system? Similar in many respects to the Gabbet-Fairfax Mars.
The Calico's helical magazine? That concept looks kinda familiar too.
And then of course, there's the novel idea of putting a little safety nubbin in the middle of the trigger face...