There have been proposals/rumors from tons of big names:
- J Michael Straczynski (Babylon 5)
- Bryan Singer (X-Men, House MD)
- Ronald D Moore (Deep Space Nine, Battlestar Galactica)
- Sam Raimi (Xena: Warrior Princess, Spartacus: Blood and Sand)
- Seth MacFarlane (Family Guy, American Dad)
Out of those, I know Seth MacFarlane understands and loves Star Trek, J Michael Straczynski created a masterpiece of sci-fi, but might not be suitable for Trek's style, Bryan Singer helped create House, which has the ideal format for a new episodic Trek series, and Sam Raimi has done some good TV over the years.