What's with XP, Vista and Longhorn? Where's windows Longhorn

Windows XP and windows Vista have a little bit of difference. Actually, Microsoft breaks windows Longhorn into smaller parts rather than release it as a full OS. The most important feature, WinFS (windows file system) has been delayed and these drag the whole Longhorn's release date into 2007. But, windows Vista without the WinFS, are going to be released in 2006. And that makes Vista just like a XP service pack 3. With the two features of Avalon and Indigo. Well, there's little differences between XP and Vista without the WinFS. It's not much an upgrade anymore, just several updates.