The blood-dimmed tide is loosed, and everywhere
The ceremony of innocence is drowned;
The best lack all conviction, while the worst
Are full of passionate intensity.
In general, people talk about what they’re confident of, and keep quiet about what they’re not confident of. There are areas where this can make sense; if I ask which Bond came between Roger Moore and Pierce Brosnan, there’s an excellent chance that the person most confident of the answer has the right one, so it’s best they speak first.
However, a question such as “what does the long-term future hold for humanity” is affected by innumerable unknowns, and no very confident answer to this question can possibly be warranted; at best we can hope to make antipredictions. If we follow standard conventions, we will thus stay silent on such matters. The only people who do speak will be those who think they know what’s going to happen; we will leave the entire subject of discussion of humanity’s long-term future to crazy people. I don’t think that’s a good idea. We see the same pattern in politics; the people who have the best judgement are exactly those who appreciate the uncertainties of these things, but all decision making is driven by the very confident; no-one fights for a measure they’re not sure will improve things.
We can only get out of this trap if we can energetically pursue courses of action we’re not sure about; if we are able to lack all conviction and still be filled with passionate intensity.
Minds aren't magic 
It’s hard, if not impossible, I think, to hold beliefs about the world sufficiently lightly that you can change them should you obtain fresh evidence that points in another direction, but at the same time hold them with passionate intensity.
(And I’m amused at myself for wanting to put in ‘I think’ as a caveat after I’d said anything so definite as ‘impossible’.)