Joomla 3.0 Alpha 2 has been released few hours ago. This version is NOT SAFE for production environments but early adopters and add-on developers should start testing this version.
Of course upgrading production sites from previous stable versions of Joomla is still not recommended. The main goal for this current release is to allow advance testing of the new admin and site templates based on the Bootstrap framework. This release also includes most of the platform changes that will be included with CMS version 3.0.0. Some of these changes will require small changes to extensions.
Joomla 3.0.0 (general availability) is due to be released on or about 26 September 2012.
Download: Joomla 3.0 Alpha 2
Users (administrators) will get the possibility to install any compliant language pack through the Joomla! Extension Manager without searching files on JED - this new feature will be available in the Joomla! 2.5.7 and Joomla! 3.0 releases.