The You Tube video below says that this is a "previously un-heard speech" in 1967. However, listening closely, this seems to be a variation of the Remaining Awake Through a Great Revolution speech he originally gave at Morehouse College in 1959, and at several other occassions, up to with his very last sermon, given at the National Cathedral in D.C. on 3/31/1968. See
and
https://seemeonline.com/history/mlk-jr-awake.htm
This may seem to be academic nitpicking, but I think it emphasizes your point. Like the Bible, Dr. King is often quoted out of context. Like the Bible, we should not just read or listen to his words, but study them. There are common themes throughout, and there are new ideas and visions which we can hear growing out of the progression of these speeches and writings.
In that last sermon, Dr. King talked about the Poor People's Campaign, which was derailed by his murder. But he concluded that speech with a vision "to hew out of the mountain of despair the stone of hope." If I may be so bold as to quote the last words of that last sermon, calling us to carry on his work:
"God grant that we will be participants in this newness and this magnificent development. If we will but do it, we will bring about a new day of justice and brotherhood and peace. And that day the morning stars will sing together and the sons of God will shout for joy. God bless you."
