The last couple centuries have seen the most significant changes in technology and means of transportation. Before rapid transportation was available, races, cultures and languages were preserved and segregated geographically. In Europe, you could travel a mere 100 kilometers before unveiling a different language and completely different culture. With the many different methods of rapid transportation available, it’s simple to get to the other side of the world and back. It’s only a matter of time before everyone in the world becomes one race.
Third world countries may slow down this process, but I believe the eventuality will be one race and some day even one language. With technology and the Internet ever evolving, the need to have a common language will become much more apparent.
I believe this will take hundreds of years to happen, or maybe even over a thousand years, but I think it’s inevitable. The real question isn’t how long it will take to happen, but whether or not human existence will be around long enough for it to happen.