Thanks for the patch, it is indeed straightforward. Two comments though:
1. i think sendReply is equally confusing (in a different way) and my preference would be inOut. Since this is what happens anyway, the exchange will be InOut, it is imho clearer what the semantics of this option is. Or, if you want, you can have it as a String instead of boolean and call it mep (better then just pattern I guess, with possible values inOnly or inOut with the former being the default).
2. You are now a committer, so please free to commit the code unless you have doubts in which case attaching a patch or adding a link to a git branch is ok. I doubt you had doubts in this case .
One more thing. I am not sure if this is necessary, camel-netty being fairly new, but if you want to just deprecate @sync, you can mark isSync() and setSync as @deprecated and have them get/set inOut (assuming you will use that instead of sendReply).