As I said in a previous post, it would be great to have an automatic and precise retopolgy tool.
Like the Mudbox retopoly or Wrap 3.0
http://www.russian3dscanner.com/
It would also be great to have a working and interactive boolean system like hardmesh 2.0.
http://www.hard-mesh.com/
This two new feature along with the quad draw system would make Maya basically the best modeling software on the market (or at least the fastest).