It depends on what you mean by "cryptocurrency". None of the Chaum-based Digital Cash system designs of the 80s and 90s featured a public ledger, but they weren't decentralized. The public ledger was an innovation of Bitcoin (as far as I know, even Szabo's property title system didn't propose to make the ledger actually public), and many people at the time felt that it was a bad idea, since it gave up anonymity.

It seems plausible that fully homomorphic encryption will eventually enable a practical and fully anonymous cryptocurrency, but nobody has figured out how yet. Also, even without FHE, maybe someone will figure out how to make a Bitcoin-style public-ledger system that somehow uses Chaumian blinded keys instead of ditching anonymity entirely.