with the PoW algorithm using too much energy for mining.
The PoW system is used by most other major cryptos as well, and equally secure implementations of PoS systems and other systems are nowhere to be found as of yet.
If you want to trade on exchanges you almost always trade against Bitcoin instead of USD
Most major alts (the ones which aren't designed primarily for pump and dumps) can be traded on some of the available exchanges against USD.
I therefore hope that exchanges will adapt USD as the standard measure and stop having Bitcoin/Altcoin pairs...
This could be a huge problem for taxation and it would require more complex KYC procedures for those who only want to trade crypto. Many of these people would prefer to stay anonymous or pseudonymous.
It's a lot more effort trading directly with fiat.