Mars may not have the water some people had hoped to use for hydrogen production and human consumption.
Reflections under the Martian South Pole may not be water, as some scientists suspected. Instead, it may just be reflective rocks.
Elon Musk wants the population to be 20 billion so we run out of space on this planet. Earth is it. That's all we get. Any pipedream of extra terrestrial mining won't take place in your grandchildren's great-grandchildren's lifetime.
Before they mine Mars, they will start on the Moon. Also, and not happening anytime soon, moving an ore laden asteroid into orbit will be more profitable than exploring an entire planet for possible ores.
Elon Musk? Is he the genius that is worried Earth doesn't have enough people?
As for extraterrestrial mining, I suspect it will be here sooner than you suggest, but we'll never know...
Why so pessimistic?