I usually avoid making bold statements but my experience in this field might for once compliment and backup my guesses as to what Redmond constantly proves is able to surprise the tech community even down to the people who believe they are joined at the hip with Microsoft believing anything they say is "sacred"
Longhorn won"t ship before 2005, So that leaves a 4 year "gap" and I really don"t believe that Microsoft will wait 4 years to release a desktop version of Windows (ie: Windows .NET server family does not apply here).
The speculation until now would have you believe that we won"t be seeing anything until 2004 possibly 2005. This is based off the whitepaper that Neowin first published back in January and April 2002 where technologies for 2004/2005 are discussed for integration into Longhorn. This would seem to validate the 2004/2005 ship date, but it"s flawed. Windows XP was also built to integrate seamlessly with technologies at LEAST 2 years AFTER its release in the case of Windows XP: 2002/2003. This goes without saying that a white-paper is more of a guideline and is never expected to be the sacred document to base all dates upon.
We will see Windows XP Service Pack 2 (SP2) in the summer of 2003 which cannot be compared to a OS release, its more of a refresh. What we will see is an XP Second Edition (XP SE or Windows XP 2004) which has been speculated (and then retracted) by a site deserving of respect yet will go un-named. This will include further enhancements to the Graphics User Interface (GUI) add DX9, WMP9, the .NET Framework v2 that is required by Avalon to integrate Office into Windows and possibly the first Yukon technologies to the file system. Some functionalities that will be absent in the free Service Pack upgrade (SP2)
So my friends. We will have a new Windows to play with come fall 2003 and it will no doubt build on the eye-candy of its predecessor Windows XP and give us all something new to play with (did I hear Sidebar?)