The threat is in the form of increasing global warming which results in climate change. Generating Bitcoin requires a capable computer to solve complex mathematical puzzles and high electricity consumption. so that some countries prohibit mining for several other reasons such as in China and Iran some time ago. if so will bitacoin and others be able to run forever or is this just an excuse to change the green field to red..
Even for those that ignore the environmental damage of Bitcoin Mining.
The literal collapse of a power grid because bitcoin mining exceeds the safe capacity of that specific power grid,
is the ultimate danger to all people on the same grid.
If their is a heat wave or subzero temps and multiple bitcoin mining operations,
their is very little wiggle room as excess power capacity is now gone.
At best this means rolling blackouts to preserve the power grid from being fried.
At worst, the rolling blackouts don't save the grid and transformers are destroyed,
this means the grid will be down for years, before full operations are restored not days.
That is the ultimate danger of Bitcoin mining , is making entire regions unlivable by power grid destruction.
Which is why China and Iran stopped the bitcoin mining as it was in danger of collapsing their power grids.
Because even Government officials admit protecting their people is more important than protecting a proven proof of waste system call Bitcoin mining.
FYI:
Go turn off the main circuit breaker to your home, and leave it off for 24 hours
now you can't cook, your lights are out , the cold or heat become unbearable without electric heat or air,
you can't use your computer, your phone charge is out, the food in your refrigerator is ruin, if you had any medicine in the refrigerator it is also ruin, no running water. In other words your life has become a living hell without electricity.
Now imagine , this will be the way it is, for 2 years, and now you understand the real danger of bitcoin mining to you and your loved ones.