Indeed the C63 was missing, I forgot about it !
2010 Acura TSX

1971 AMC Javelin AMX
1973 BMW 2002 Turbo (pretty much confirmed by the Jalopnik Studio Tour)
1984 BMW M635CSi
2010 BMW X6M

1970 Chevrolet El Camino 454 Super Sport
1964 Chevrolet Impala SS

1982 DeLorean DMC-12
1971 De Tomaso Pantera
1986 Dodge Shelby Omni GLHS
1992 Ford Escort RS Cosworth
1987 Ford Sierra Cosworth RS500
1992 GMC Syclone

2010 Gumpert Apollo (Speed ?)

2009 Holden HSV W427

1982 Lancia 037 Stradale

2010 Lotus Evora Type 124

2010 Mazda(speed ?) 3
1977 Mazda RX-3SP
2010 
Mclaren MP4-12C
1990 Mercedes-Benz 190E 2.5-16 Evo II
2010 Mercedes-Benz C63 AMG
2010 Mercedes-Benz SLS AMG
2011 Mini Coupe
1988 Mitsubishi Starion ESI-R
2010 Peugeot 308 (RCZ ?)
2010 Renault Mégane (RS ?, RS Cup ?, Trophy ?)
1977 Saab 99 Turbo
2010 
Subaru B4 2.5
1987 
Toyota MR2 Supercharged
1988 Toyota ST165 Celica GT4
1983 Volvo 242 Group A Homologated
I added the approximative missing dates. I also added the possible versions for the cars which came for the auction house leak because the names in the AH are often shorter than the real names. Seeing as Turn10 tends to get the best versions of the cars (all the Skyline in the game are Spec-V versions), I supposed that the Apollo could be the Speed version for example. There's no sporty version of the Peugeot 308 which leads me to believe that this could be the 308 RCZ that we're talking about. Same for the Mégane, I don't think Turn10 would add a simple Mégane dCi to its roster. It has to be either the RS, RS Cup or Trophy.
As for the Mazda 3, I think that when a Mazdaspeed version exist, they get that in the game.