The only downside is that Ripple isn't resistant to quantum attacks and the threat of this kind of attack in the future is very real.
I would love Ripple to go into partnership with Quantum Resistant Ledger as I am sure that would make even more major players adopt their platformif they could future proof the security of their platform.
It's very simple to add a new signature scheme to Ripple. We did it to add Ed25519 support. You don't have to change your Ripple address and accounts that use different signature schemes can interoperate seamlessly.
If we added a quantum-resistant crypto scheme now, we'd be stuck with it forever. And all of the currently-known such schemes have massive downsides such as very large public keys.
It just makes a lot more sense for us to wait until there's some reason to think it's needed. We could easily deploy a new signature scheme in 3 months (or faster if the need was urgent). We think it makes more sense to choose a scheme as late as safely possible to give us the most information and best choices of what scheme to adopt.
But we watch closely.
If anyone knows of a quantum-resistant signature scheme that permits multiple signatures and has performance and key sizes not much worse than Ed25519 or SECp256K1, that could change things.