Support for HTML 5
This would allow the new HTML 5 standards to become utilized. Such as adding buttons to the control panel that allow the designer to add video and audio content with the ability to modify their properties.
+1 to Buz's suggestion - adding support for HTML5 elements.
Actually, just being able to add the Cushy CSS classes to HTML5 elements such as <section> or <article> would be great, too!
Had to change my sections to divs in order for them to appear in the (awesometastic) Cushy editor
Would also be nice if data attributes could be used for description info instead of id & title:
<section class="cushycms" data-cushy-description="Primary article at top of page">...