Musk also explained how his colony would get to the point where it can reliably refuel spacecraft all by itself. Dragon capsules would serve as scouts, helping find the "best way" to extract water for fuel reactions. An unmanned Heart of Gold spaceship would then deliver the basics for a propellant plant, while the first crewed mission would finish that plant. After that, SpaceX would double the number of flights between each ideal Earth-Mars rendezvous (every 26 months) until the colony can reliably produce fuel by itself.
Oh, and don't worry about today's Falcon 9 rockets being consigned to the history books. Although the main booster for interplanetary travel will "have an easier time of things," Musk believes that the final iteration of Falcon 9 (Block 5) could be used "almost indefinitely" if properly maintained. Production on Block 5 should fly in the next 6 to 8 months.
SpaceX is still a long way from explaining the nuts and bolts of large parts of the Mars mission. You won't learn about the Interplanetary Transport System's habitation section for "a year or two," for one thing. However, this at least shows that Musk and team have thought about the minutiae of their plan -- the big challenge is following through on all those promises.