Like 99% of altcoins, this is not going to move the needle and not going to amount to anything more than a publicity event. Miami coin isn't going to be popular and isn't going to increase adoption meaningfully. The one thing you can say about it is at least Miami is trying something far more advanced than any other place in the US, but don't expect it to have a material effect on anything bitcoin related.
I think it will be a normal currency, like any other alt, that's how you say it, in this case no alt has a life of its own, the only currency that has a life of its own is BTC, without BTC there would be no alt. Miami can launch a cryptocurrency, but it will never be much stronger than BTC, it is something that does not make any sense. What happens is that BTC is always mentioned for the value of the currency, because it would not have any point of comparison.
Perhaps now as everything is focused on cryptocurrencies, it is very easy to launch one to capitalize money in a simple way taking advantage of the boom, it is very common, also a currency created by a state, or a government entity in my opinion will never be trusted.