Unfortunately, we don't have anything else to go on besides this single, relatively uncertain image. Then again, we're having trouble coming up with any other realistic ideas about what this might be.
Sure, there are some possibilities like Pompeii 2, Grand Ages: Rome 2, Gods and Heroes 2, History Channel Great Battles of Rome 2, The Republic of Rome 2 (for all we know it's a remake of Ceasar 2) but we can't see those games being teased on the back page of a magazine.
It's much more likely that we're getting a sequel to one of the most highly rated strategy games ever made. Which is awesome. July 18 can't come soon enough.