Inventing a superior gene doesn't itself make them a new species. They only become a new species when the result can't breed with a base human. However, even

Inventing a superior gene doesn't itself make them a new species. They only become a new species when the result can't breed with a base human. However, even that gets fuzzy--there's a "species" of bird whose name escapes me that lives in high latitudes. They can all breed with the neighbors, but birds from the two ends of the span can't breed with each other. I expect to see the same thing happen with humanity--eventually highly modded individuals won't be able to breed with unmodded individuals. (Although, unless immortality is developed there won't be any unmodded individuals to breed with. Why would the genetic engineers care about compatibility with the old version that's no longer around?)