ErraiBus now has it's first async IO implementation for Jetty Continuations. It is implemented in the class: org.jboss.errai.bus.server.servlet.JettyContinuationsServlet. The old servlet is now referred to as: DefaultBlockingServlet.
You can specify the implementation now (optionally) int he ErraiService.properties like so:
errai.servlet_implementation=org.jboss.errai.bus.server.servlet.JettyContinuationsServlet
The addition of true asynchronous IO did require some substantial work to the plumbing of the MessageBus, actually. In order to facilitate it properly, I had to add support for thread workers, so messages could be delivered asynchronously. But all-in-all, seems to work great.
Mike