For the iPhone (iOS4.x) version Sony will have to submit it to Apple and await their approval. So I suspect the Android version might appear first. But that is just a guess.
However, I'm not anticipating any more than another lackluster phone app by a major reader manufacturer. The Kindle and Nook apps are lackluster. Plus Sony cannot even produce a decent Reader Library app nor a decent Reader Store website. Sony is about hardware and they do that very well, but their software tends to be terrible.