Wot-news.com made a summary article, what waits for us in 2013. I don't think it's an official Wargaming text (can't see source quoted anywhere) - still, it's good. Main points:

- according to the developers, 2013 will be all about team competitions and e-sports
- 7/42 companies will be implemented
- 2013 has 6-10 patches planned (2 of which are out already), new tanks and maps are planned for most (perhaps each one) of them
- up to 11 new maps are planned for 2013
- 0.8.5 will have the German medium branch (VK2001DB, DW, VK3002DBv1, Indienpanzer, Leopard prototype, Leopard)
(SS: also apparently the 3 Soviet light tanks: T-60, T-70, T-80 at tier 2, 3, 4 probably)
- 0.8.6 will bring the new Soviet medium branch and possibly the replacement of T-50-2 with MT-25
- tier 9 and 10 arty - early autumn, after that the British arty will come
- premium Type 59 will not return regularily, might be a part of events/special sales, but the Chinese premium heavy WZ-111 might make an appearance
- Japanese tanks will appear either at the end of this year, on early next year, some of them are confirmed to have autoloaders
- replay mechanism will be changed this year too, replays will be stored at WG server