I quote myself ...
30 weeks left 'til the end of the year, 10 cars released in the DLC in March ... Looks like time for some releases

One thing I saw by lurking around under google :
http://www.virtualr.net/assetto-corsa-version-1-0-content-list
In this list appears a "Content to be patched in" section, where we can see that Zandvoort would be planned, aswell as some other nice things. By insisting a little, I found this :
http://www.redbull.com/en/games/stories/1331718396849/italy-s-gran-turismo-meet-assetto-corsa
Telling that there will be a "Bonus Pack" free including 5 cars + Zandvoort in a couple of monthes (interview is one month old), and the Dream Pack 2 that will include Lambo + Audi + Surprise + Circuit of Catalunya