Fedora Core 6 will reach its end of life next month. From the Fedora mailing list:
A reminder to users: Fedora Core 6 will reach its end of life for updates on Friday, December 7, 2007.
Fedora 7 will remain supported until one month past the release of Fedora 9 (as things stand, this would be roughly through the end of May, 2008).
- The Fedora Board