Yes, on April 15 is when the US version goes on sale.  The disc version is rumoured to have extras such as video course guides of the tracks from real life and that GTTV could have the option of users showing off their laps and tuned cars!  Polyphony Digital, the developer, has said that all regions will get this update at the same time!  This could mean an update for the EU on or before the US release! 

Caption: This is a picture of GT TV on GT5:P