After they have conclusively proven the success of their large launcher with countless launches to get all the equipment and supplies in orbit and the SpaceX mission leaves for Mars what is SpaceX going to do? Sit on it's laurels and wait for the mission to reach Mars? Or maybe allow anyone to launch massive payloads into space on a very well proven platform.

If SpaceX can show they are have a very capable platform for heavy lifting before anyone else they can retain that position for a long time. Moon bases, Hubble replacements, long term space stations all need heavy launch capabilities. SpaceX wants to sell them their premier service.