My layman's understanding of the situation is that the most likely first use of this in humans will be for personal eugenics of one's offspring. Meaning, removing deleterious genes from, or adding beneficial ones to, your sperm or egg cells in a lab and then implanting an embryo.
My non-layman's prediction is that you are quite incorrect. As others are pointing out, successfully using CRISPER/Cas is hardly as trivial or as easy as the media's hype machine (or university PR offices) would like us to believe. Blatantly obvious ethical issues aside, embryos are hard to tamper with, and the odds of successfully achieving multiple edits to the genome are miniscule.
I think the most likely first application of the CRISPER/Cas system in human medicine will be in an autologous bone marrow transplant to correct a genetic disorder of the blood, likely sickle-cell anemia.
Immunotherapy is likely a clear win for this kind of genome editing technology. Any sort of ex vivo modification and repatriation of cells (like bone marrow transplants) are a good fit.
Personal eugenics is extremely unlikely in the West. It is also very far away because of this regulatory burden. Id just point out that there are cases where you might find this kind of thing permissible. For instance the other day a friend of mine who went through IVF with his wife said "imagine if we had one good embryo from three rounds of IVF, and that one embryo had cystic fibrosis - would you really be comfortable stopping me from repairing that?"
I found it hard to say "yes we should stop that". But I also recognise that if we allow that, its only a small leap to allow anyone to edit anything they want, for whatever reason. Drawing the lines will be tough.
For the deal I mentioned: http://www.xconomy.com/boston/2015/01/07/cart-crispr-1st-of-...
I'm not suggesting tampering with an embryo - rather, editing the sperm or egg cells. I don't think the ethics is going to stop people when there is a chance of giving your offspring a significant advantage. But like I said, this is purely from an "outside" perspective - I don't know much about the field.
Contrast your prediction of elective eugenics for offspring with my own for autologous bone marrow transplants for sickle cell anemia: sickle cell is a single point mutation, there's a lot of tissue that we can sequence and work with, you don't need to transform anywhere near 100% of the tissue to get a good therapeutic effect, and we already do cure sickle cell anemia with bone marrow transplants given the right circumstances. All of that is in part why I think you are completely wrong with your prediction.