I'm wondering the same thing. It looks like it would. Remote Buddy-->iTunes-->airTunes speakers-->AppleTV-->stereo.
I've said many times that if the AppleTV could rent movies and if I could access my music through my iPhone (use it as a remote), I'd get one. Maybe this is the ticket?
Whether or not Remote Buddy does it now, I'd expect this functionality to be available from *someone* post-SDK. Perhaps Remote Buddy itself will offer a native iPhone client-app.
I'd expect a lot of apps to ship with an iPhone companion-app soon.
Edit: Now I see what you're saying. I don't think it talks directly to AppleTV yet. If it's true that the AppleTV will act as airTunes, it's a functional workaround, nonetheless.