From the Apple release:
Apple is transitioning away from Xserve. Xserve will be available for order through January 31, 2011. After that date, customers looking to upgrade, replace, or supplement existing Xserve systems with new Apple hardware have the following two server solutions to choose from.
Those two options are Mac Pros and Mac minis. A lot of people will be annoyed by this, it is a very interesting decision.