The only thing I've heard is them saying there was "100 tracks," which I'm sure includes tracks that are just flipped, so you drive them in reverse, or in some cases a slight change in the path you take, but overall it's the same track.
I saw the conference and when they were giving their "definitive racing game" speech they said over 100 tracks in the final game but then I read somewhere about the 30 tracks with 3 variations for each track, still like I said I think it's plenty and sometimes reverse tracks are more challenging which is even better.