At this point there is no definite knowledge about the EQ2 interface besides that it will be different from EQ1. We are pretty certain that it is still in XML, but how it is put together, what can be modified, and if any apps for modification is being provided is unknown.
You might try going over to the EQ1 side and checking out the guides/messages for making UIs. Try building a EQ1 UI. This will give at least a basic knowledge for fiddling with XML for when EQ2 comes out.
edit:
http://www.eqinterface.com/forums/faq.php?
Best of Luck