The 2011 Citroen DS3 Racing was a leaked car in Forza Motorsport 6, but was never released. It appeared in a leaked video along with the 2013 Caparo T1 and the 2013 Cadillac XTS Royale 70 Limousine.
I noticed T10 are adding manufacturers back in their latest, such as the 2CV, which belongs in Citroen, is back in Forza 7 after FM5. Now Kia is coming back after FM4. Sweet!
Also, love the look of these cars. Wonder how they will perform when they arrive in Forza.