Being an optimist, I'd say never. I really think we (I'm thinking here of the Christian West) need to grow up and throw out some cultural trash. And I just can't see that ever happening .... But ... there is hope yet.
In the form of China and perhaps India. But I'm thinking that China will be the one to take the next steps. To the moon To Mars And that when they do, the west will follow suit, lest they be relegated to 2nd place.
As for exoplanets. Earth does not have the technology to even send a robot probe to another star system. I'm guessing it will take hundreds if not thousands of years to develop robots that can repair themselves, And those robots are so intelligent that they know that they need to be repaired.
And they are so completely stocked with spare parts and raw materials, that everything that breaks down will be able to be repaired. Suffice to say we are not even near being able to do that.
It will never happen because we are home. We may one day have the technology to do it but we will not do it when the probablitly of finding a home like earth. Earth is very unique with its avrage temperature the soil composition and the wabble on its axis.
The bioloigical make up of our plants and the way they grow will not be the same on another planet with a bigger or smaller star. The light frequency may be different. A planet may spin slower or faster.
In the end every last detail of our planet would have to be just right for humans to colinize another planet and the problem of finding a planet is greater than any techonoly we may need.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.