Wargaming.net has not one, not two, but three action MMOs in its portfolio. You've probably played World of Tanks, and World of Warplanes just recently transitioned from alpha to closed beta. The company is also working on World of Battleships as well as a portal to connect all three World War II titles and allow gamers to access them instantly.
The service is called, er, Wargaming.net Service. Once it is deployed, players will receive unified Wargaming.net IDs "that will provide instant access to all games and services, as well as any partner or fan websites."
The company's latest press release also mentions something called a "single MMO battle realm," where tank, warplane, and battleship clans will assist one another in their quest for world domination.
[Source: Wargaming.net press release]