I can actually see a world where many people use stablecoins just like that long into the future that have a floating exchange rate with Bitcoin.

There's just tail risk to using them that most people won't notice, so they'll be really widespread and very well advertised. Although not great, it'll still be better than what we have, and it'll ease the long transition to bitcoin's dominance for small payments, which should take a long time to mature and maintain the base layer ethos as much as possible.