If the record is beaten much earlier than this, I suspect it would be some combination of the following two things: undetected doping, or genetics. Genetics further breaks down to good luck (a new mutation; see earlier article about how this may actually confound endurance sports); better recruitment (many credit Germany's dominance of soccer to this, but running as a sport just doesn't command the profits to accomplish the same thing); eugenics; and discovery of pre-existing genes in previously isolated populations. Maybe there's a group in Tibet or highland New Guinea just waiting to whoop the marathon world's ass! What I don't think will cause an early sub-2 is non-doping training innovations. We mostly seem to be chipping at margins of mature training techniques. A little taking advantage of altitude here, a little better nutrition there...will that really get us there so soon?
As an aside, the importance of human capital in the modern world is demonstrated by this caption from a photo in the article: "The biomedical lab at Addis Ababa University contains hundreds of thousands of dollars of equipment. But because of insufficient funding and a lack of available experts to operate it, much of it is unplugged and covered by tablecloths."