Patch 0.8.10 - containing the preliminary Japanese technology tree - is planned to come out later in December, with the test server set for this Thursday (the 5th).
Patch 0.8.10 is planned to come out later in December, around the 23rd for the US/EU servers, with the test server set for this Thursday (the 5th).
The biggest change is of course the introduction of regular Japanese vehicles into the game, which will feature several light tank plus a full medium line. From what information is known so far, they will have generally poor armour, but good guns (with excellent gun depression) and decent mobility. A branch of heavy tanks is planned, but isn't being introduced just now as WG have decided that there aren't suitable vehicles for all tiers yet.
Other changes coming include graphical improvements in several areas, mostly with regard to lighting and shadows; a change to the way some penetrable objects work (such as brick walls and fences, where the shell will now go through but with some loss of penetration); and the introduction of a new map called Hidden Village, alongside the rebalancing of several existing ones.
To see a full list of the preliminary patch notes (which may of course be subject to change), please click here