If we must have crypto, then Bitcoin will eat stablecoins' lunch
Assuming that most of the world switches from statist fiat money to some form of voluntary cryptocurrency, there is zero chance that a stablecoin will prevail over Bitcoin.
Bitcoin Lightning is better money than a stablecoin on Bitcoin Lightning, for the stupid obvious reason that a money which depreciates less is, ceteris paribus, better than a money which depreciates more. Thus, ceteris paribus, no one with two neurons to rub together is voluntarily going to prefer a depreciating money over an appreciating one. Let me repeat that: unless coercion perverts the future market for money, the choice is obvious — only dumb people would voluntarily choose a worse money; of course, in a voluntary social order, dumb people are free to piss their own wealth away by choosing bad money.
This idea that money needs to have its purchasing power perpetually perverted down (the whole point of the "stable" euphemism in "stablecoin") is a statist / Keynesian idea, i.e. a bad idea that only serves the Cantillonaires. This bad idea will die, along with the constellation of bullshit statist epicycles around it — "deflationary spirals", "economic stimulus", "easy money" — when Bitcoin adoption kills it. These bad ideas will be to future economics as alchemy and phlogiston theory are to modern chemistry today.
Stablecoins will be unnecessary in the future — they will be remembered as fossils from the inflationary era Bitcoin left in the dust.
1 BTC = 1 BTC