A trip to Mars is a stretch goal that we need to start as a species. We know that our lifetime as a species is limited on earth so the sooner we start figuring out how to get off the planet the better. Yes, we might fail but then we'll have to try again and again.
Musk has made himself the spokesman for that task. No one else seems to want the job. Yes, he's a dreamer and might be overselling the task but that's what we need. We need to start. I can tell you that if we never try it will never happen.
My hope is that he becomes so rich that he owns all of Mar's resources. Yes, he'll own them for a bit but it means mankind has made a large step forward. Go Musk!