Yeah Amazon still runs on Coral, there were some recent (release a few years ago) advances on it under the hood and ergonomically. I think the "replacement" for it is Smithy[0] though it will likely just replace the XML schema and codegen and not the protocol. Honestly at this point I think it would be in Amazon's best interest to heavily invest in Java Project Loom rather than trying to convert to async.
[0] https://awslabs.github.io/smithy/