The same question was asked some years back when Wiggins was the leader and Froome the aspiring champion. At some point Froome attacked pethaps to demonstrate that he was ready to take over from Wiggins but he fell back in line. You can't win the tour by yourself, Sky is in a great position in case Froome falters and I imagine the director is coaxing both riders but the rest of the team will continue to support Froome unless he shows cracks and Thomas will eventually fall in line. I would be very surprised to see them duke it out in the time trial