via r/xboxone
http://www.purexbox.com/news/2016/05/forza_motorsport_6_to_get_licensed_nascar_expansion_pack
http://www.purexbox.com/news/2016/05/forza_motorsport_6_to_get_licensed_nascar_expansion_pack
The reverse of the card reveals that the expansion will contain a NASCAR World Tour Career Mode, 24 new cars from the 2016 NASCAR season, new multiplayer events, new display elements "for improved drafting and car spotting" and a new course - Homestead-Miami Speedway.