Microsoft have reversed their decision to not release any more versions of separate from Windows, and have announced they are planning on releasing beta versions of IE 7.0 this summer.
Previously Microsoft stated that the only future releases of IE would be bundled and presumably integrated into future releases of Windows, such as Longhorn, which may be released next year (2006).
One can only guess that they are feeling pressured to keep up the maintenance and security updates, and are also feeling pressure from the widespread adoption of Mozilla Firefox.