It is official now: a demo of Need for Speed SHIFT will get released!
It will feature two tracks, the Spa and the London River and 5 cars (Dodge Viper, Lotus Elise, BMW M3 and Nissan GTR unlocked initially and the Pagani Zonda after winning all the races and getting all the stars). You can expect it on all three systems - PC, PS3 and Xbox360.
Expected release date is late September / early October.