Phen0m at the Kunos forum did a nice collecting job of al info that is known about the future dlc content for AC. Original thread here (subscription needed):
http://www.assettocorsa.net/forum/in...-thread.19313/
Dreampack DLC:
Nürburgring Nordschleife
Sauber Mercedes C9
Corvette C7R GTE
Nissan GTR GT3
Alfa Romeo 4C
Alfa Romeo GTA
Alfa Romeo 155 V6 TI
McLaren P1
McLaren F1 GTR
BMW M235iRacing VLN
Mercedes 190 E 2.6-16 Evolution 2
Free Content after 1.0 (released when ready):
Zandvoort
Monza 1962
Silverstone Historical 60's
Nissan GTR Nismo
Corvette Stingray C7
Abarth 595ss vintage
Abarth 500 Assetto Corse (race car)
Toyota GT86
Alfa Mito Quadrifoglio Verde
Scuderia Glickenhaus p4/5
Audi R8 Plus (2014)
Audi S1 Quattro
Lotus Exige R-Cup
SC P4/5 Comp. 2012 Hybrid
Future DLC content (content which has been announced but without release/DLC info)
Circuit de Catalunya
Toyota Supra MK IV
Toyota Celica
Toyota AE-86
Toyota GT-86 GT4
Toyota TS040 HYBRID
Lambo Aventador
Lambo Huracan GT3
Lambo Asterion
Lambo Miura SV
Lambo Countach
Lambo Gallardo GT3
Lambo Huracan LP620-2 Super Trofeo
Lambo veneno
Lambo Gallardo LP 570-4 Superleggera
Ruf RT 35 S
2015 Ford Mustang
Ford GT
Audi R8 LMS
Possible future content but not 100% sure (yet):
Brands Hatch
Audi R18 E-tron Quattro