Make the case that universities are threatened by the rise of free online education (as I have) and you’ll quickly hear a laundry list of the extra benefits that make a university education superior. But what you’re really hearing is the death knell of the traditional university model.

The term “disruptive innovation” is thrown around a lot these days, including in the context of education, but I’ve been thinking more lately about what it really means, having recently read a profile of HBS legend Clay Christensen as well as heard him talk at TEDx Boston.

In Christensen’s model of disruptive innovation (he coined the term) the response but a university education is still better is just what you’d expect to hear. According to Christensen, innovators typically start out in the lower end of the market, making cheaper, lower quality products for consumers previously excluded from the incumbents’ products. As the innovators slowly creep up the market, the incumbents retreat to the high end, a process that continues until the incumbents are displaced. As he wrote in his seminal book on the subject:

“Generally, disruptive innovations were technologically straightforward, consisting of off-the-shelf components put together in a product architecture that was often simpler than prior approaches. They offered less of what customers in established markets wanted and so could rarely be initially employed there. They offered a different package of attributes valued only in emerging markets remote from, and unimportant to, the mainstream.”

The example he often talks about is the steel market, but I’d argue we’re seeing this exact phenomenon in education. Online educational opportunities – from OpenCourseware to Khan Academy to Udacity and Coursera – don’t yet function as a substitute to those seeking a prestigious degree. But they’ll certainly drive people who just need to learn something away from universities.

We’ll see people who don’t need the stamp of prestige or who previously couldn’t get into universities (especially prestigious ones) using these tools instead of the one-off university course or the professional certificate. Universities will start to abandon their continuing education programs, and they’ll claim that the high end of the market – undergrad and grad degrees – is the important and lucrative space anyway.

But the online ed disruption won’t stay at the bottom of the market for long. It’ll knock out grad degrees maybe, while universities claim their real advantage is the broader cultural role of college. Or maybe they’ll capture the intro class market while the universities claim it’s the really meaty, advanced stuff that they do so well.

It won’t happen overnight. But next time you hear an argument as to why universities can’t really be replaced by online ed, listen closely and hear the typical disruptive innovation story playing out.