Seriously, do an extension search online of all the X3 announcements starting from the time X2 was released until the release of The Last Stand.
There's a pattern there.
The main problem came when X3 all of a sudden slowed way the hell down...even after X2 was a serious hit at the box office and critically acclaimed.
Look at what happened from Spider-Man to Spider-Man 2. 2 to 3 months after Spider-Man came out, Raimi and his team were already at work on Spider-Man 2.
Look at what they did with Spider-Man 3. A few months after Spider-Man 2 hit theatres, they were at work again, knowing that Spider-Man 3 was coming out in 2007, not 2006. Spider-Man 2 came out summer of 2004.
Why the long, long wait to greenlight X3. What the hell did Fox do in all of 2004?