Mac OS X 10.6.6 has been released for developers only. Though OS X 10.6.5 is not out for public, but Apple says that this beta release is for developers to focus on new changes.
Contains developer support for fetching and renewing App Store receipts. See “Validating App Store Receipts” for more details.
The download size of 10,6.6 is only 3.7 MB. This beta release also indicates that public version of 10.6.5 is very near to release.