Verse 6 is very interesting to me...
For they have shed the blood of saints and prophets, and you have given them blood to drink. It is what they deserve!" (Rev 16:6)
Taking that together with...
so that the blood of all the prophets, shed from the foundation of the world, may be charged against this generation, from the blood of Abel to the blood of Zechariah, who perished between the altar and the sanctuary. Yes, I tell you, it will be required of this generation. (Luk 11:50-51)
"Woe to you, scribes and Pharisees, hypocrites! For you build the tombs of the prophets and decorate the monuments of the righteous, saying, 'If we had lived in the days of our fathers, we would not have taken part with them in shedding the blood of the prophets.' Thus you witness against yourselves that you are sons of those who murdered the prophets. Fill up, then, the measure of your fathers. You serpents, you brood of vipers, how are you to escape being sentenced to hell? Therefore I send you prophets and wise men and scribes, some of whom you will kill and crucify, and some you will flog in your synagogues and persecute from town to town, so that on you may come all the righteous blood shed on earth, from the blood of innocent Abel to the blood of Zechariah the son of Barachiah, whom you murdered between the sanctuary and the altar. Truly, I say to you, all these things will come upon this generation. (Mat 23:29-36)
I think Revelation may be speaking of the fulfillment of the judgment that Christ promised would happen to the generation that He spoke to.
It's even more compelling when we see that the word translated "earth" in this chapter can also be translated as "land"...perhaps a reference to the "Promised Land"