This is tricky. Some may see it as Bush doing what he said he wouldn't: establishing a withdrawal schedule that would tell the insurgents how long to wait. But I see it as a message to non-insurgent Iraqis who are also unhappy about foreign (and non-Muslim) troops on their soil. The message is that we don't plan to take over their country, but plan to leave as soon as the situation is stabilized to the point where we are not needed, and we talk about when that might be if all goes well. But we don't really give a withdrawal plan like we did in Vietnam (or like Israel is doing with Gaza), a declaration that we are gone as of a certain date, regardless of the security situation at that time.
Which I never understood anyway, because what's to stop them from just waiting until they see everyone leave? If they wanted to wait, they'd wait. They know we're gonna leave sometime.