Apparently Windows Server "Longhorn" (the next release of Windows Server) will be known as Windows Server 2008 when it is released. You can read more about the 'leak' of the OS name here: http://blogs.zdnet.com/microsoft/?p=434, if fact even Wikipedia mention that the name will most likely be 2008: http://en.wikipedia.org/wiki/Windows_Server_%22Longhorn%22.
IISxpress 2.1 has been tested with Beta 3 and works just fine and should continue to work just fine with the final release when it comes along.
Now all we have to do is wait...