We're going to need to finish this upgrade for version 5.9, or alternatively rather than binding to JGroups directly we could use the WildFly clustering API.
In that second option we'd benefit from some nice features from the clustering subsystems, like clustered singleton deployments and decoupling from the specific JGroup version used in the server. The drawback would be that people not interested in WildFly would not be able to use this specific backend.