Although it's not BBM 6.0, Research In Motion has released an beta update for BBM 5.0.

This update comes in version 5.0.3.13.

I know everyone is wondering what's changed.

The following explanation is provided in Beta Zone:

The short answer? Nothing that you can really see. We've made a few minor back-end fixes to the application and would like to make sure everything is working just fine. You may not see any of the bugs or feature requests you reported for BlackBerry Messenger v5.0.2 addressed in this build, but don't be discouraged! Rest assured that we've received ALL your feedback and it will all be taken into consideration for future versions of the software.
Although I do love official/beta releases from RIM, I think I'll keep my BBM 6.0 leak for now.