You keep current and retool like all successful people. If you are not adaptable and not committed to lifelong learning and skill development, you die. That is true in computers moreso than most any other field. That’s why I stopped being a true engineer in mid-career. It is brutal keeping up with new graduates.
I see what most of what the F1000 companies are doing w big data and analytics — this is not a fad. It is as fundamentally transformational as computers, networking, and the Internet were in the last big waves.
But a student needs to step back and look at the systems rather than learn specific technologies up front; e.g. Hadoop.
The retooling that I have done has been much less painful because I am able to see big pictures. For instance, when HyperCard came out on Macintosh computers in the late 1980’s I learned it inside and out (on my own). It was my first introduction to object level programming and hyperlinking for data management. This was before HTML or the internet. It was before the big object level programming languages arrived. But I was prepared.