The number one thing is performance improvements in the various areas. Some things are very simple.

-dynamic hair and cloth
-soft-body dynamics
-enhancements in the usability for animation and rigging
-improved performance mainly with animation and scrubbing
+optimize c for hi mesh figures
+improve memory usage
-improve displacement- also being able to apply to domains
-better previews
+Better shader management dealing with application and use of multiple shaders on domains.(more tedious than need be) Like shading grps
-Tie it in better with hex, (fix hex) or include in c6
-Be able to save a configuration file for prefs to reload your prefs much easier
-True intuitive baking
++Real full UV tools or fix hex's
+Continued improvements in volumetric lighting options
-multi-pass options in rendering
-scripting or macros

No need to think outside the box....
    Just make it invisible.