When I researched the GT3 release (that happened BMGT - Before MasterGT), the release date (esp. in Europe) was reset until the very month it got released.
Europe basically got it at the same time as North America. Similtaneous release would be nice, but don't count on it.
PlayStation Europe is the only area that currently has a release month (Sept.), Japan has "2004" and SCEA doesn't even know what GT4 is, so, like I said, don't count on any of that being accurate.
You will most likely play it before Christmas, unless it is wrapped and under a tree.
Cheers,
MasterGT