In case you don't know, Longhorn is the code name for the next version of Windows, which will replace Windows XP.
Although it itself does not contain it, this latest build strongly hints at a new file system, which shall supercede NTFS as the file system for Windows. Called WinFS, this new file system [COLOR=royalblue]"promises to do away with hierarchical storage altogether and remove the distinction between local and remote storage...."[/COLOR]
Exactly how this might be implemented is still a mystery, but perhaps doing away with drive letters altogether, and instead using mount points as UNIX does might be on the cards. Windows 2000 and XP already have mount point technology, but doing "away with hierarchial storage altogether" smacks of even bigger changes than the loss of drive letters.
One opinion floating around is that in much the same way that Windows 98 included Internet Explorer integrated into the operating system in order to gain a competitive advantage over Netscape, Longhorn might integrate a next generation SQL server into the operating system, in order to gain an advantage over Microsoft's arch rival Oracle. This next generation SQL server could be integrated into the file system, a sort of SQLFS, if you like.
Longhorn will likely retain support for NTFS in much the same manner that legacy support for FAT32 and FAT16 is available in Windows 2000 and XP. Longhorn is also likely to include a number of other enhancements over Windows XP, in the areas of security, multimedia, etc, as well as an integrated download manager.
The latest Longhorn build is circulating on some dodgy IRC channels right now.
More here, and here.