im not sure i 100% agree with his plan though. i think before we start martian colonization i think we need an industrial complex on the moon to extract fuel, water, and manufacture and materials for colonization craft. which i think would be a better investment. it could service satellites, space stations the like because it is probibly cheaper to refuel them from the moon than it would be to launch new ones or refuel from the earth. and of course competition between lunar refuelers and earth refuelers would drive launch and transport technology forward.
once thats out of the way then go to mars. infrastructure then colonization. also we need to get away from chemical rockets for interplanetary craft, get things like vasimr working, and develop better power systems to allow for their continuous operation. this is probibly the nearer term thing too, as vasimr is due for in-space testing in 2015.