Good news...Longhorn client is officially targeted for 2006, with the server to follow in 2007. Even better, Avalon (graphics subsystem) and Indigo (communication subsystem) will also be available on both Windows XP and Windows Server 2003, meaning that developers will be able to target millions of machines with these technologies. In order to deliver on this release timeframe, the next-generation storage subsystem known as WinFS will be made available after Longhorn availability. The target is to have WinFS in beta around when Longhorn is widely available.
See http://www.microsoft.com/presspass/press/2004/Aug04/08-27Target2006PR.asp for more information.
Good stuff to look forward to.