The apparent meter that circles the icon in the upper right corner of the full screen (not pictured) is now three-quarters full (it was one-quarter full to start and was filled to halfway upon the first update), suggesting that the next update will display a full meter and perhaps the ultimate reveal. (DLC? Spin-off? 3D Blu-ray movie? It's anyone's guess.) The icon itself is thought to be representative of the Spartan army's shield; the upside-down "V" being the Greek letter Lamba, standing for "Lacedaemon" (what the ancient Greeks called Sparta).
So who is this mystery man? He certainly looks like he could be angry. And anger has always fueled this franchise, which still has some venting to do.