However, humanity lives in an increasingly global environment, and natural selection works slowly - so no two generations will be able to draw a line saying "they're a different species," so they'll still likely call themselves human. And they'd still be our descendants, so I don't know why we wouldn't still think of them as "us" in some way. I don't see a split in what is considered "human" unless we do become an interplanetary civilization, because then it's conceivable that groups of humans could be removed from contact with the rest of humans, and end up evolving in a different direction. Though I wonder how much convergence there would be anyway, given that we save people from a lot of things that could keep them from passing on their genes. I think there will be a wide range in what is considered "human."