Release dates tend to be a contrivance of the publisher and it's marketing people, whilst meanwhile the developer keeps begging for more time. There's almost always that "one more thing" that the developer/support staff are wishing to tweak, or another map to add, etc.
Consider yourself lucky when content or patches are added to a game you are interested in. VUG pulled the plug on support for Tribes:Vengeance almost immediately upon release, then waited for months to admit it, having promised all the while a patch that was never to come.