5DIII is a great all-round camera, but of course I could be tempted to upgrade.
Smaller and lighter, improved DR and high ISO performance
Improved video performance with features like focus peaking, false color, really good AF.
To be honest, I'll probably add a crop body to my 5DIII, and/or C100 mark II if it's really good. Pretty happy with stills, but could use improvements in video area.