There are not enough planes to populate another 10 tiers not only for nations that stopped development, like Germany, but for all others.
Depending on method, jet fighters from tier 8 are classified as 0 or 1st generation - high speed subsonic. Tier X are 1st or 2nd generation - subsonic or even transonic (later versions, for example F-86 is claimed to bypass speed of sound in shallow dive, but it wasn't announced for political reasons).
Then there are supersonic fighters with AA missiles - something that WG said will never happen (at least supersonic speed seems to be a serious limitation of game engine).
And after tier X there are about 5 generations: 3,4,4+,4++,5, and there are about 5 5th generation fighters all around the world: F-22, F-35, PAK-FA, J-20 and J-31. Well, F-35 can be split on 3, but still there are only 3 nations with such planes: USA, Russia and China.