As was alluded to in the comments, my colleagues at Blockstream Research are doing some work on this with mechanisms called SHRINCS and SHRIMPS.
Of course, inventing and demonstrating a quantum-resistant signature mechanism isn't the same thing as deploying it in consensus or upgrading everyone's UTXOs to it, and it's fair to say that there are many steps in between!
Of course, inventing and demonstrating a quantum-resistant signature mechanism isn't the same thing as deploying it in consensus or upgrading everyone's UTXOs to it, and it's fair to say that there are many steps in between!