While; yes, the world is changing fast and so are our weapons, but the probability of a worldwide nuclear war is low due to the fact that no country leader would be stupid enough to launch a nuclear bomb at either Russia, UK, or USA. I'm not saying war won't get worse and more fearful, but full on nuclear war is beyond us, the US has allies with several countries, so if one country attempts to attack one city or several, their allies will retaliate with them and fight them off. And the term "weapons of mass destruction" is very dull, because the actual blast radius of the average atomic bomb is 14km, and the ffallout is about 20km, (not only that but the actual chance of a bomb landing in the us is very low due to our naval defense.) If you were to completely wipe out all life in the UK, it would take over 7000 nuclear warheads.
As for the second one, there's not much we can do about this, it's pretty much how the world works all around, in a few hundred years, yes; countries will fall and rise, there's no stopping it. It's how the Roman empire fell. But, just one economic depression will not make the economy fall completely, we've gone through them many times before.
But yes, they are "probable" but not likely.
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