Here is some more stuff I have found about X3 on Xmenfilms.net:
"Firstly, there have been rumors amongst the fandom that "Wolverine" may be filmed before X3 - that's false. Finishing the X-MEN trilogy is the top priority of 20th Century Fox, but spin-off films are being developed at the same time. As most know, "Wolverine" and "Magneto" are also in early development.
The studio is set on getting X3 out for a 2006 release. Even though Avi Arad or Marvel Enterprises has listed a May release date, the month of May has been put in question, so changes in release date are a strong possibility. It all depenRAB on the director and shooting locations. A Winter 2006 release is not even being thought about, so nix that idea."
So at least it looks like it should be out for 2006!