It's less medical and hygenic advances that are slowing evolution in humans as it is airplanes. The constant travel and mixing of all different groups of humans is assuring that the gene pool is incredibly large and thus it is very difficult for change in any specific direction to occur (for any alleles to go to fixation). Also, the sexual selection for non-deterministic traits (ie, personality) is lessening the effect of biological evolution on humans.
Genetically speaking, we are one of the most healthy species on the planet. For most of our genes, we have a wide range of alleles that are now in almost constant reassortment. These variable alleles make us, as a species, more adaptable and less susceptible to infectious disease. And, as long as our numbers remain in the billions and no groups really isolate themselves, evolution will be very, very slow.
That being said, a trans- or post-human future is a definite possibility. Given our tendency toward egoism, I doubt that many people would consider this 'evolution' but I, for one, would. It's one of the two real futures I see for the human race (people have to get real about traveling to the stars). The other is some calamity (a plague, a meteor, more likely a nuclear war or drastic climate change) that kills most of the people on the planet. The attendant destruction that panicked people would visit on the earth makes it likely that most people remaining would eventually be pre-agricultural societies. And then evolution could proceed. But I think humans will survive, in one form or another, no matter what. We're pretty adaptable - like big cockroaches.
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