After committing these verses to papyrus, the Jewish people went on to become the only tribe to ever engage in a truly global diaspora, somehow retain their unique ethno-religious identity, and go on to retake their ancestral homeland. Moreover, the scribes who penned these verses managed to pass on their fundamental religious and cultural memes to at least 7.5 million Bahá'í, 14 million Jews, 1.6 billion Muslims, and 2 billion Christians. Not exactly "all the families of the Earth" but those are damned impressive statistics for a particular collection of ancient memes, the contemporaries of which are today almost entirely extinct.
I will make of thee a great nation, and I will bless thee, and make thy name great; and thou shalt be a blessing...and in thee shall all families of the earth be blessed... Unto thy seed will I give this land.
Back to the story. Abram sojourns around a bit, and ends up in Egypt during a time of desperate need. If this sounds familiar, it is because the story will be retold time and again throughout the Bible. Note especially the narrative elements of Egypt, famine, Pharonic dialogue and dialectic, and that "the LORD plagued Pharaoh and his house with great plagues," which is a bit of a bloody giveaway that the authors of the narrative (and the Author of the Universe, as some would have it) do not mind heavy-handed heapings of foreshadowing. At the end of this particular pericope, the Pharaoh finally stops sticking it to the prototypical Jewess, and lets her people go.
One really can't blame the poor Pharaoh too much, because Sarai was really quite a "fair woman to look upon" as they say, and while a later Pharaoh was to suffer the affliction of a divinely hardened heart, we can fairly assume that this one was quite naturally smitten with a different variety of personal turgidity.