Currently there are tanks from four nations in World of Tanks (ignoring Premium tanks). Initially it was the Russians, Germans, and Americans, and in a later update the French were added (in a scaled down tech tree). In the 7.4 update coming probably in June the French tech tree is going to be expanded. However, today Wargaming.net have revealed what the basic British Tank tech tree is. No doubt this will be expanded in due course as well, and I have to say I am quite looking forward to be able to play a few British tanks. No date as to when this will happen, but my guess would be October-December time. That said, it is quite possible Wargaming might pull this one out of the hat earlier.
I read quite often on the forums that many folks want other aspects of the game to be improved, rather than new tanks. Ignoring for a moment that the people coming up with new game modes will not be the same people developing new tanks, I have to disagree. New tanks bring a bit of variety into the game. They are different, sometimes surprisingly so, from each other. There is also a rather fun element of playing “your” nation’s tanks, I think. This is one reason why I am looking forward (long way down the road) to when they add a tech tree of the tanks of various other nations who had some tank production.
For now though I will wait and anticipate playing through the British line.