It's new and very exciting game from Wargaming.net (Order of War, Massive assault). World of Tanks is a huge mixture of multiple genres. First of all this is an MMO game allowing thousands of gamers from around the world to test their tanking skills. When developing the game, we did not want to link it to a particular genre, that’s why World of Tanks depicts a combination of such genres as the third person action, FPS, RTS, RPG, and the simulator. Any gamer will find WoT pleasant to their own favor. He will get highly detailed tank models, hardcore battles, and, most importantly, the atmosphere of shoulder-to-shoulder fights with brothers-in-arms against a well-organized enemy. Details: http://www.worldoftanks.com/
The game will be released in Russian and English. Russian beta testing is already in progress, as for English one, it will be started in the near future.
In addition - here's a big devs' interview about the coming game: http://www.massively.com/2010/03/22/interview-with-world-of-tanks-mike-zhivets/