In terms of politics; I see the multitude of laws to be the greatest flaw to be considered in the next hundred years.
A politician is also a "lawmaker" making the situation very dire
for individual freedom. The more useless laws, the more outdated
laws left on the books means a overly restricted society and even
a change in Government where we are mainly puppets to the whims of
Government.
In terms of global warming; we'll be around in 100 years but our
technology has led to a situation where millions will die as a consequence. Will we learn to fix the damage that our pollutions have caused the eco system in a hundred years. Let's hope so.
That's my opinion right now.