Black Swan events may not be "predictable" in the sense that the exact date of their occurrence is known. But black swan events are all imaginable, and have frequently have been seen in science fiction literature, or some other fictional and non-fiction writings preceding what was thought to be a black swan event. Also, what is a black swan event to some, (eg the Japanese after the first atomic bomb) was certinly not a black swan event to the US military, which knew very well what the consequences of the bomb were, planned, and executed the event. Maybe a better definition of black swan events would be those events that are extremely unlikely or unexpected to a particular group of people.
The example of the Sept. 11 disaster comes to mind, where many of the top US officials claimed that nobody could have imagined such a thing. But this was a lie, since such events had already been depicted in comic books years earlier, and there were even intelligence reports that such a thing was being planned. (predictable by the terrorists, unpredicted by the US)
Another example is Pearl Harbor, Dec. 7, 1941. again there was intelligence that this was being planned, months prior to the event. And moreover, a fictional book was published in the 1930's descibing a Japanese attack on Pearl Harbor. (predictable by the Japanese, unpredicted by the US)
In another example, the appearance of Cortez on the shores of Mexico was not a black swan event for the Aztecs, since there were legends in the far past of the Aztecs that bearded men (gods) had sailed east from Mexico with a promise to return. And that was why they at first welcomed the spaniards and were so docile at first.
Also, if black swans can be imagined, then you can "back engineer" what would be needed for such an event to occur, and then watch for "warning signs" of such events in order to calculate that the event has a higher probability.
A database should be established of all imaginable black swan events with literary references where they exist. This should be done for future black swan events, as well as, past black swan events. All science fiction should be scoured and anayzed, as well as all other fictional and non fiction books, especially written by futurists, prophets, and others. I am sure that the military has already done this, and if they have not, they certinly sholud do it.