I would put > 50/50 odds on there being a human alive today with at least one CRISPR-edited germline variant. I think the question is now how can we regulate/control CRISPR germline editing; not how can we prevent it.

Human embryo gene editing was reported in May 2015 (http://dx.doi.org/10.1007/s13238-015-0153-5). It's reasonable to assume that the editing took place significantly before the submission date, especially given reports that the paper was first rejected from several other journals on ethical grounds (http://www.nature.com/news/chinese-scientists-genetically-mo...). I'm not trying to suggest that these particular scientists have performed experiments on viable embryos also, but I'd be very surprised if someone hasn't.