Coming out today, for free, the 2015 Mustang is coming to Forza along with several other cars.
http://news.xbox.com/2014/08/gamescom-forza-motorsport-5-new-cars
August free car pack:
2014 Renault Spark SRT_01E
2014 Rolls-Royce Wraith
2014 Infiniti Q50S
2014 Infiniti Q50 Eau...