No government would ever allow coins like Monero to become main forms of currency. The potential for abuse and tax evasion is just too high. They would sooner ban them outright. No legitimate business would accept them then.

Accepting random alt coins would also come with the expense of having to track them and their wallets separately, exchange costs, volatility, etc, so over time just a few will become generally accepted by businesses.

And yes, the most likely consequence of long-term crypto usage is that users will centralize into a few trusted platforms who will get the Lion’s share of tokens and power.