I wonder whether the focus on content and dates aren’t a huge factor here? It seems like the truly useful things we learn from World History are the commonalities among all human societies, and the ability to analyze historically. If we focus on content rather than skills and discovery, we automatically focus on chronology. In the long run perhaps it will be possible not to use dates, but themes or topics or techniques that go across time. Until then, perhaps one can teach from whatever date to the present making sure that each piece of content is put into context (which of course would mean going back to the history before that date).
As for the preparedness, it may be best to acknowledge that knowing world history is simply not possible, in the same way that knowing any history fully is really not possible, in terms of content. But it is possible in terms of overarching themes, comparative history, cross-cultural connections, and so much more. I wonder whether the preparation couldn’t focus on that instead of content which, in today’s world of easy search, can be found to use for evidence or argument, rather than memorized. In looking at what the content cutoff dates are, we seem to have lost sight of both the ease of access to factual information and the basis of history in the humanities. Both the AP test and the teaching that results from it are too concerned with content over historical method or purpose.