Just picked up some info that 3 new cars will be released for Forza 3 on Nov. 17th via a free DLC car pack.

2010 Genesis Coupe ‘SPECIAL’ [Hyundai Genesis Coupe Pack/FREE/Nov.17th'09]

2010 HKS Genesis Coupe [Hyundai Genesis Coupe Pack/FREE/Nov.17th'09]

Forza 3 - Downloadable content

2010 Rhys Millen Racing Red Bull Genesis Coupe [Hyundai Genesis Coupe Pack/FREE/Nov.17th'09]

Rhys Millen - Forza 3

So now we have some official drift cars in the game, not just liveries.