Kool is there are alternatives - and I mean besides the cyber ones. Relying on fiat currencies is not pretty kool at all.
Methinks we'd need a 3X PhD in economic theory to come in here and set the record straight, because all I see are economic "armchair quarterbacks" spewing a lot of junk about how great cryptos are compared with fiat, and how they will take over, without understanding the global dynamics of money (currency) and what it represents. (Think progressive millennials with their smartphones who do not know what a dial-tone is.)
Even though I like decentralized currencies, unfortunately, cryptos only exist at the mercy of centralized governments who use fiat. The internet infrastructure that crypto relies on and physical businesses that take crypto all exist within the territorial confines of centralized govs who enforce and regulate it with military force. So far cryptos have been allowed to exist as sort of a cute experiment, if they ever get mass adopted to the point of causing a noticeable dent in taxation, the gov will likely crack down and ban the usage and mining of cryptos by people, businesses, and sites that reside in its territory. Even if crypto servers were setup in antarctica to avoid centralized govs it would have no military backing and could get crushed in an instant by a willing central gov, and the only way to avoid that would be to get their own enforcement power which ironically would make it centralized like every other currency. Furthermore there is nothing proprietary about a specific coin, even bitcoin, whose technology can easily be duplicated as a ton of copycat coins and shady ICOs have sprung up recently. the only thing that keeps it as the "main" and most liquid crypto is its brand name and popularity, whimsical aspects that have no real military power of enforcement in case real world stress tests starts.
all you have mentioned are either centralized govs or striving to be their own centralized gov with their own power enforcement over territory
None of those are decentralizing in the libertarian cryptocurrency sense, 3 of them use the pound, catalonia would still use euro, and kurdistan if it ever exists will probably still use dinar or switch to euro. They would all seek to regulate the financial infrastructure and enforce laws and taxations in their territory as well.
If those moves come to pass let's see what currency they each use. Catalonia for instance, Spain would not be happy if EC allows them to continue to use the Euro. Who knows. I don't, but then neither do you.
You forgot the most important property to be the "main": it's the most safe and secure, because it has by far the most number of Accountants (mining power and nodes) and smartest Developers. Cryptocurrencies are in a constant and never ending war. Every moment attacked by hackers from the inside as well as governments/banks/haters from the outside. All wanting to grab a piece of the exponentially growing market-cap, which grows just because (and as long as) it can withstand these attacks and innovate in even more robustness. Bitcoin flourished for 9 years already in this extremely hostile environment, and is the reason it is the "main".