The 7th gen doesnt strictly exist... In terms of hardware it is identical to the 6, but it has software version 1.2 on it. If you own a six, it costs money to update, but if you buy a 6 after the release of the 7 then the update is free.
I think the 7th gen name is more of an internal thing, as hardware suppliers were changed, but hardware specifications stayed the same. Basically the icons got a bit bigger and not much else.