The rate at which Bitcoin consumes power isn’t even sustainable now. So in 50 years, something will have changed, or Bitcoin will have ceased to exist.
That's a little harsh. Bitcoin mining takes as much electricity as a small country, but the reason for mining being to hard it strong competition. And I don't think this problem is big enough for bitcoin to stop existing.
It may even be that they decide to completely outlaw Bitcoin in their countries and go down the route of government-issued cryptocurrencies.
Outlawing bitcoin and other top cryptocurrencies means not only making millions of people angry, but involves a high risk of underground economy that will have more negative effects on national economies than some regulations making usage of bitcoin 100% legit.
In general, I think this article is just too negative about btc and its future.