This new update will include 20 new tanks for your armory, such as the "nimble Chi-Ha light tank, well-rounded Type T-34 medium tank, and the devastatingly powerful IS-2 heavy tank". As well as the variety of light, medium, and heavy tanks, the new content will include Premium tanks too.
The new update is available now for the Xbox 360 version. The Xbox One version of World of Tanks is due for release on July 28th. You will have the same states on the Xbox One as the Xbox 360 when moving over.
Crossplay also a new added feature. :)