Most all futurists will tell you that it is rather easy to predict 5-years in advance 50% of the time, and 10-years out 25% of the time, and the chances of being right about the future much more than that go down drastically each year.
Some will say it's due to the Black Swan Events, other say it's because things are just too complicated now in the present period and things will be even more complicated in the future.
Just ask Ray Kurzweil, who proclaims the Singularity Theory that will take prediction and throw it all out the window.
Let me recommend a very good book where someone goes out of their way to give it their best shot in predicting the future; 100 years from now: "The Next 100 Years: A Forecast for the 21st Century" by George Friedman; Doubleday Publishers (2009).
He shows how Mexico will emerge as a strong nation due to its birth rate and demographics and proximity to the US, an aging population in need of labor amongst other future probabilities in the author's crystal ball.
How does he come about all these epiphanies? Well, as he explains in his book, he looks at all the trends and how they will interact with one another.
He also proclaims that the United States' economic power and strength will be passed by eventually, but it will not be anytime soon.
The projection of military power that the US presently has will keep it the only super power for a good additional 20-years.
Now I do not wish to give away the whole book, but I would like to recommend it to you on this fine day.