Sounds plausible enough, and the pessimist in me definitely agrees. Let’s hope I’m wrong!
I don’t know… I certainly don’t see BTC staying around for the next two decades because it has substantial flaws in its protocol (see next paragraph). As for other crypto I don’t really see it happening because a) I doubt people in power will want to give up the possibilities fiscal policy allows for and b) the natural way of crypto is ‘screw up and there’s no going back’ might is too scary for many people.
Regarding the flaws in BTC: The problem is actually that there is limited supply. Paper with better explanations here. Since miners at some point will only make money from transaction fees, they will only mine part time: Only when enough transactions have saved up to make mining worth it. Certainly not great for stability…
Second flaw: Any economically thinking miner will mine where most transaction fees are available. This is called PettyCompliant in the paper. Because of that, intentionally not processing all transactions becomes the optimal strategy, leaving an ever growing backlog of unprocessed transactions outstanding. If a miner does not do that, then noone is incentivized to mine on top of his blocks.
Short version: BTC will slowly stop processing transactions unless people run miners because it’s fun.