Magento 2 is slated for a Q4, 2012 release.

Magento 2.0 runs on PHP 5.3 and the Zend Framework.
jQuery Replaces Prototype.
The default prototype library will be replaced with the jQuery.
Better Model Component-Oriented Architecture
It will be a completely new architecture and a code base. The various modules will be components with high code coupling between each other. The Magento directory structure will also change.
EAV
- Magento developers tend to simplify, to make the product as massive.
-The new version will not include EAV, and it probably will not be in the directory.
-Developers will have to rewrite modules
-Magento 2 retains the three model, helper, and block factory methods. Magento 2 has done away with the alternate group/class-name alias structure.
Multiple DB Support.
Magento 2 will be supported by MSSQL, Oracle and is expected to support PostgreSQL soon.
Speed
Magento 2 will be faster than ever, reducing the time to generate the pages on the server and also optimize the page load times in browsers.
Automated Testing
Magento 2 will come with a set of automated tests for Unit Testing, Integration, and Functional and Performance Testing

The code is also available at Github