I am much more excited about the possibility of making a Big Freaking Hauler version of the ITS second stage and sending a few hundred tons to LEO for 100 million dollars or so. We could basically start sending a new space station up per launch, or a few hundred tourists. This would revolutionize space tourism in the short term, and would also make manned missions to a bunch of planets cheaper and accessible.
On the whole sustainable colony part, the truth is that mars is "just" a low pressure big desert with nothing special to do. It will be fun to see the footage of the explorers, but I don't really see enough there to justify a massive spontaneous migration. People keep comparing this to the migration to America, but in this case it is more like trying to make a similar scale migration to the middle of the Sahara desert. Madness I say.
Once you get to mars you are basically stuck in a bunch of structures built inside a desert. People would have as much incentive to buy a one way ticket to mars as they have today to buy one to live in Antarctica. And still there are very few people there, and that is even though they have freaking penguins. So.. there is really no real driving force for people to pay so much to move to such a hostile environment(be it Antarctica or Mars).
Elon's billions could surely start a small science colony on Mars, with a refueling station and maybe some tourists, but I doubt there will be that many people interested in the one way tickets he needs to create the sustainable colony. At least not for quite a few decades. I doubt it will happen as quick as the presentation implied(as in, this century), unless it gets a lot easier to get there(and stay there) quite quickly due to breakthroughs in science, which I can't quite predict when will happen.