Stevens talk at Full Frontal was absolutely fantastic, one of the best I have ever seen. I highly recommend watching the video once it comes out. It is very impressive to see such complex topics being presented with such ease and style.
I among others will work on the dev-jqueryui branch in June. I hope we will manage to stabilize it and merge it to dev in this time.
It should be noted that we plan to make the ui an optional part of Aloha (with default being a jqueryui implementation) to make it easier to integrate into existing systems. The heavy extjs dependency is part of why Aloha is so huge.
I also plan to look into using google closure compiler in ADVANCED_OPTIMIZATION mode to shrink the size to the absolute minimum.