From All About Microsoft
"Windows Vista is not fully baked, but that doesn’t mean senior management isn’t already thinking about "Vista+1" as they like to call the next Windows client release (the one I believe is — or at least was — code-named "Fiji").
Read the rest here
Not really surprising, you always have to be one or two steps ahead in this day and age of software development. Another factor why Microsoft could also be in the very early planning stages is to push out technologies that they have been incubating for years that could be easily released by a competitor before Company even has chance to make users aware of it. Also, technologies that did not make it into Longhorn because of time constraints or just was not ready such as PC Syncing, Vector based UI or Castles might just appear in this future update of Windows. Still, I am not excited about it, I am more anxious about Vista RTM, Ultimate Extras and Vista SP1.