As noted by MacGeneration , Apple has announced it will be discontinuing the Xserve as of January 31, 2011. The note appears on Apple's site and links to a PDF titled "Xserve Transition Guide". In the guide, Apple explains that they will not be developing a future version of the Xserve.

Apple will not be developing a future version of Xserve. Xserve will be available for order through January 31, 2011. Apple will honor and support all Xserve system warranties and extended support programs. Apple intends to offer the current ship- ping 160GB, 1TB, and 2TB Apple Drive Modules for Xserve through the end of 2011 or while supplies last. Apple will continue to support Xserve customers with service parts for warranty and out-of-warranty service..

The two alternative server solutions include the Mac Pro with Snow Leopard Server and the Mac mini with Snow Leopard Server. Apple provides transition considerations for customers migrating from the Xserve to these products.

The Xserve was Apple's rackmount line of Mac servers which was first introduced in May, 2002. Apple has kept up with mostly annual updates to the line. The last update for Xserve was April, 2009.