Because of the value of Bitcoin, people will hoard it,
On the contrary, people will choose other cryptocurrencies because it's cheaper than BTC in the hopes that it will also rise in value.
~ There may be cryptocurrencies becoming legal tender, but not now, volatility and supply and demand need to be considered.
Although some of its citizens are not in favor of the decision, the El Salvador government already declared BTC as a legal tender. There are also news articles that says legislators in other countries are proposing to do the same. Before all that, Japan already recognized bitcoin as a payment method.