This is currently not possible, but I think it's a good idea. We could support returning a Future in remote interface methods. Would you mind creating a JIRA for this?
As an alternative you could use conversational messages (server messages delivered to a single client in response to another event) using the MessageBuilder: https://docs.jboss.org/author/display/ERRAI/Conversations
Note that this won't work for conversational CDI events as there the worker thread would have to reply directly (conversational context stored in ThreadLocals).