cheap high-throughput DNA sequencing is going to change the world in a shocking way (by 2020, I think). at present, it's not crystal clear how; there's a lot of nonsense speculation being thrown around and it's not easy to separate the legit potential applications from the bogus. After all, there have been many new technologies in biology that have been touted as the technology that will cure disease.
For example, microarrays were supposed to inform differences in gene expression (i.e. how much of a given protein is being made from a given gene) between, for example, a normal tissue sample and a tumor sample, and thereby identify the cause(s) of cancer. The bogusness: 1) this reasoning requires that cancer is caused by change in gene expression (dubious), and 2) that there would be sufficient statistical power to distinguish such a change from the intrinsic measurement error (equally dubious).