As I see it, we’re on the threshold of taking charge of our genes through genetic modification. Add to that the fact that we will scatter like spores throughout the solar system (and especially the asteroid belt), and in 3000 years we will have the entire solar system populated by different alien races that will all trace their origins to humans.
We won’t need to explore the galaxy for aliens, we will create them.
As for humans on Earth, we will probably all look the same for a very long time, but maybe a little healthier.