Nope, no new cars or tracks. Dont believe everything you read on wiki, people change it / make it up ahaha
They did add cars and a track on the spec II update, if you don't believe me then here's proof
These are the spec II cars and tracks that were added on.
High Speed Ring
Amuse S2000 GT1 Turbo
Art Morrison '60 Corvette
Aston Martin DB9 Coupe
Blitz Dunlop ER34
BMW 1 Concept Series Tii
Citroen C4 Coupe 2.0VTS
Concept By Gran Turismo Cappuccino/HP Tuned
Concept By Gran Turismo Clio Sport V6/Tuned
Concept By Gran Turismo Corvette Zo6/Tuned
Concept By Gran Turismo Elise/Tuned
Concept By Gran Turismo Elise 111R/Tuned
Concept By Gran Turismo Ford GT LM Spec II Test Car
Concept By Gran Turismo Gran Turismo 350Z RS
Concept By Gran Turismo Evolution IX/Tuned
Concept By Gran Turismo Evolution X/Tuned
Concept By Gran Turismo Skyline Coupe/Tuned
Concept By Gran Turismo Swift Sport/Tuned
Concept By Gran Turismo Viper SRT-10 Coupe/Tuned
Dodge Viper SRT-10
Ferrari 512BB
Ferrari F2007
Ferrari F40
Ford Focus ST
Ford GT
Honda NSX Type R
Mazda RX-7 Spirit R Type A
Mazda RX-8 Type S
Mine's BNR34 Skyline GT-R
Mini Cooper S
Subaru Impreza WRX STi Type RA
Suzuki Cervo SR
TVR Tamora
Volkswagon Golf V GTI
These cars and tracks came on the spec II update, and I didn't get this from Wiki, it tells you what cars and tracks were added on in the Gran Turismo 5 Prologue official website