It means that I think it will eat all money (and most altcoins as well) over the next 15-20 years.

About the downside: I hope using coal as an energy source will be shut down ASAP. Bitcoin protocol would easily work with only sustainable energy sources, but it doesn't work without the security of proof of work (all other algorithms for decentralized concensus so far decrease security of the protocol).

Luckily China already took some steps to close down the most polluting Bitcoin miners.

Existing (non crypto/legal tender) also has environmental downsides. Is there a serious study comparing the environmental downside of currencies (crypto and not crypto)?