No cryptocurrency will ever come even close to scaling to the billions of transactions each day by people worldwide.
That's a bold statement. You can't possibly know that. We're not talking about the next 10 years, but ever. How do you know what people will use for currency in 2050, or 2150?
IMO it's not going to be fiat currency and if not that then what? Maybe we'll be mostly extinct and back to trading seashells and amber, but if not we'll not use currency printed by FED. There will not be any FED, I'm pretty sure of that.
I don't think that there's any danger to bitcoin. The only danger is that there will be no anonymity, but for that to happen they'll first need to ban cash.