[Ed. – Why wouldn’t it be?]
Is there a Homo superius just around the next corner, waiting to take our place? Let’s think about what it would take: If we were to give rise to a new species, something would have to happen to us to create a bottleneck or isolated place for a founder-person and her or his mate to show up and get separated from you and me and our offspring. In the modern world, that is very unlikely. We have airplanes and ships and the Internet.
What if there were an enormous war and all of our intercontinental means of transportation were destroyed? Perhaps then an isolated population of people would live apart from the rest of us for so long that they would no longer be able to successfully interbreed. Just listen to all the dialects we have for speaking English. When human populations are even a little bit separate, they start talking differently. Other bigger changes might happen with more profound separation. Perhaps this could happen somewhere beyond Earth, even, such as in a colony on Mars. Without geographic isolation, I am not sure we can get a new species of hominid, not ever. But that is not the same thing as saying that humans are no longer evolving, because we surely are.
We cannot step away from evolution. Our genomes are always collecting mutations, and we are always making mate selections. Are humans preferentially mating with other humans who are tall? Blonde or not blonde?