In Oedipus Rex, what does the chorus's final speech tell us about human life?

The final speech of the Chorus looks back to reinforce one of the lessons of the play -- that the future is beyond human knowledge:

Ye men of Thebes, behold this Œdipus,
....
And, lo! in what a sea of direst woe
He now is plunged. From hence the lesson draw,
To reckon no man happy till ye see
The closing day; until he pass the bourn
Which severs life from death, unscathed by woe.

In a very short time, Oedipus has gone from being a king to being a despised outcast.

However, there is a second layer of meaning to the Chorus' words. Oedipus, after all, does not die at the end of Oedipus Rex -- he goes into exile. The Chorus thus looks not only backwards but forwards, to the events of Oedipus at Colonus, which covers the death of Oedipus himself, and Antigone. In Oedipus at Colonus, the disgraced Oedipus accepts the judgment of the gods and the prophecy of the place where he will die, and so far succeeds in his penance that his burial site becomes a source of blessings and victory. In this way, he seems redeemed. On the other hand, he also curses his sons and predicts they will kill each other, a prophecy shown to have been fulfilled in Antigone with the added death of one of Oedipus' daughters and the total and unexpected ruin of his formerly triumphant nemesis Creon. Thus to the very end of Oedipus' life, and even beyond, human fortunes remain unpredictable, as the Chorus has warned.