It won't ever happen, which is too bad because I'd really like to see who they dig up for this mission. The whole project is just too expensive for a private enterprise to carry out.
However nice it might be to visit Mars, living there for the long term (meaning any longer than necessary) is going to be impossible. There is insufficient water and insufficient protection from radiation to sustain life (from earth). These explorers are going to have a limited time on Mars before they get cataracts (in the short term) and cancer (also probably in the short term, sadly) due to the massive doses of radiation they'll experience just getting there.
I guess I'm saying that they might want to think about including a return trip in their itinerary...