from the few pictures I've seen of GT4, it did so Tsukuba Circuit, which is a real in Japan. Best Motoring uses this track a lot. So I'm assuming it has to have most of all the tracks that the Autobacs JGTC uses also, which includes Suzuka International Circuit.
I could be wrong in this, we just have to wait until there's word on this to see if it's true or not.