There are certainly lots of things I would like... but I'm really hopeful MAXON comes through with an awesome Node Editor API for third party renderers and Xpresso with the new nodes.
Also I would really like to be able just drag and drop materials into a node window and have multiple materials being controlled from one node editor, just like the new Corona Node editor. I haven't used the nodes much yet, but what is the point of having all the materials types in there as nodes..you can't seem to do anything with them? So for me... the top right now. new Xpresso nodes, new node API, global node editor(if you so choose) with ability to edit multuple materials/objects. and UV, Bodypaint, and performance improvements.