Ed Spencer presented at Sencha Conference some new ExtJS 4.0 features. He also wrote a blog entry about it.
You can check out the blog entry here: http://www.sencha.com/blog/2010/11/22/ext-js-4-preview-faster-easier-more-stable/
Following is his presentation about Ext JS 4.0:
And his presentation about Ext JS 4 Architecture:
Sencha also published all session presentations. You can check them out here: http://www.sencha.com/conference/sessions/
I am very excited to start playing aroung with ExtJS 4. The release is planned for February 2011. It is going to change how we develop Ext nowadays.
Can’t wait to see it!