Classically, one requires isolation, for a new species to evolve. Today the trend is just the opposite, with greater mixing; hence hybrid vigor? Yet disease has had a strong selection effect in the past, as for Europe, Africa; this kind of selection indeed might not be over; such as for histocompatibility genes and there products. What about evolution of human nature; are we stuck with what we have? See Terrence Deacon's Symbolic Species bk commentary on brain and language evolution. If human nature is fixed more or less, but culture, such as technology, is exponentially (?) increasing; is there not then a time when humans might become irrelevant in comparison to sophisticated computers. Hans Morovec's Mind Children bk places this at 10k years, based on processor speed. However cognition is much more complicated than that; perhaps 100k to 1M years might be a better guess when homo culturus (next in our descent; a pure cultural species?) supplants us in regards to logic, rational management of planetary resources; von Neuman probes for robotic space exploration etc. Perhaps implants for us in order to deal with the dark side of human nature; so that hatred and violence ends forever. Voila!