Katmai is the code name for the next release of SQL Server and it is currently slated to be released sometime in 2008. That is just 3 years after the SQL 2005 release. A key focus of the release is a much better support for unstructured data with integration with the WinFS file system. You can read up more on katmai at MSFT’s site here and also on Microsoft watch.
And here was the press release from MSFT about katmai.
Systems Engineering and RDBMS 