I'm still betting on December 14th, since there's been no official announcement to the contrary. The argument about going gold doesn't mean so much these days, at the speed they can press CDs and DVDs. I've seen games go gold and be on the shelf a week later.
I'm also confident that PD is doing everything in their power to get the game out before Christmas here in the States. Probably not by themselves, either.. remember, PD is owned by Sony. I can imagine the conversation around July or August, most likely went something like this:
Sony: So, will GT4 be out in time for Christmas?
PD: Um.. no.
Sony: Why not?
PD: Well, we're still having a lot of problems with the online mode.
Sony: What about the rest of the game?
PD: Oh, we just need to polish up a few things, it's nearly finished.
Sony: If we drop the online mode can we get it out before Christmas?
PD: Yes, I think so.
Sony: Do it.