Half-blood elf is the term used to describe the offspring of humans and blood elves. They do not yet exist or at least no in large enough numbers or ages to be noticeable(if any they are most likely infants). Since blood elves came into existence only a few years ago, they certainly have not had time to mingle with humans and produce adult offspring — without even factoring in blood elf prejudice. This does not mean that it cannot happen, however; it is possible it might happen 20 years in the future. The blood elven half is more dominate and they have the blood elven racial traits.