Yeah, Watkins Glen is fantastic, shame you bought it on the last day of the week
With the update there's nothing set in stone yet (that won't be till basically the days around the release where they may, or may not, release the release notes before it to show what's going to be in it) but the likely things are:
New Tyre Model - Dave Kaemmer has spent over a year now I think working on improving the tyre model and it looks 'quite likely' that it will be included in the next build, initially I think it's limited to certain cars (the main ones are the top-end NASCAR cars which currently suck)
Sound Improvements - last build they added some FMOD stuff, I expect to see some more FMOD related stuff to it, incremental stuff but nice anyway
Graphics Improvements - again the last few builds have slowly been adding/changing graphical stuff, not likely to be a huge difference but it'll be there
Probably some more damage repair stuff as well, possibly the ability to stall a car but I wouldn't hold my breath for that one.
Ultimately the tyre model is the big thing, and I think everyone's looking forward to it (but will still moan when it doesn't make them an alien

) should make the cars handle/feel a lot better, which is desperately needed on the powerful oval stuff.
On the track, they announced Okayama a while back, then that it would be a free track added to the basic package (much like they added the Street Stock, SRF and Mazda MX-5 as 'free' content since I've been there), this should be complete by the next build, possibly sooner, and will almost definitely be incorporated into almost every road series for good measure
