Not with the distances and times involved unless we develop FTL communication. At first we may not diverge biologically, but culturally, and that is quite enough to close most doors... after all how many Norwegians do you find that marry bushmen or aborigines and vice versa?

A lot of sci fi seems to somehow overlook our cultural/social baggage and yet those are precisely what are crippling us now, and likely to retard our progress in the future too, if not outright destroy us.