According to this, SCEE’s confirmed that GT5 Prologue will hit Europe on March 28, priced £24.99. The precursor to the main event in GT5 is to include ten tracks, 37 cars and four modes, although details in that story are slim.
A downloadable version of the game is also expected through PSN.
Update: Uh oh. Looks as though there may be something amiss here. Just got this back from SCEE: “With regards to your query, we are aiming for a late March release for GT5 Prologue, although pricing has yet to be confirmed.”