- 906
I was wrong
From IGN
"Porsche will very likely not appear in Gran Turismo 5. Kazunori was disappointed by this fact, but according to our interview, Porsche already signed an exclusive deal for a different game and it's highly unlikely the brand will appear in Polyphony Digital's upcoming hit. Perhaps Porsche will show up in a future GT title."
but IMO that still means no.
I agree it seems like it's a 90% no, but then again, I consider PD to be just as fickle as Brett Favre when making decisions. (And this is coming from a Packer fan who still roots for #4)