From CVG:
In an interview with CVG this afternoon, Yamauchi said that the update will also have a big focus on enhancing Prologue's online modes, starting with the addition of various "community building features."
The last bit will come as particularly excellent news to PS3 owners, as the GT5 preview is currently lacking somewhat in the online department.
You can expect the full interview with Mr. Gran Turismo very shortly. Who says it's 'just a demo' now, eh?