In the past 100.000 years, give or take, the human species has seen a large amount of evolutionary changes as it spread over the globe. With the advent of modern transportation, geographical barriers to interbreeding have fallen.
My question is, will the interbreeding that is now possible be enough to keep the human populations from mutating further apart form each other or will the broad range of environments we find ourselves in produce even more distinctions?

Will there be a day when some groups can no longer have fertile offspring with each other?