It could be the beginning of a super-human race that will replace homo-sapiens, or it could be the beginning of the end for humans, as tampering with our genome could cause unforeseen mutations that will destroy humanity all together.
Both of these scenarios assume (with no basis whatsoever) that unmodified humans will go extinct.
I was merely painting a hypothetical, and not suggesting that the only potential outcome is unmodified humans going extinct. Certainly, over time the possibility does now exist. And, one can argue the basis for that assumption also exists, and is displayed all around us. We are currently the only surviving member of the Homo genus.