I have a E3 2005 and 2006 Sony conferences vids at my computer.
At 2005 Wada was at the stage, presented FFVII tech demo and said that Square-Enix is going to support the PS3 and bring the Final Fantasy to the platform. At 2006 Kaz just showed up, said that the game will be available in "multiple versions" (referring to Versus, that statement didnt make any sense actually) and then there was a trailer.
So I think it hasnt ever been announced as an exclusive at any major event. However, every time Nomura was asked in an interview about the PS3 exclusivity he replied "Of course".







