My Yuri's Revenge creation, Yuri's New Terror, consists of nearly 50 new units and 34 new skirmish modes. The AI is more advanced, and builds huge bases. All sides have many new aircraft, in fact, new aircraft account for over half of the new units! 5.0 will have even more skirmish modes, ones that are big feats of coding, because they will change and replace certain units. It'll take a long while before 5.0 is released, so 4.5 should keep you occupied!