I doubt there will be a desktop (Windows OR Mac) client; however, the fact that other "smart phone" operating systems (even the Android, which is Unix/Linux-based) do not support the HTTP Live Streaming protocol
, and with the advent of HTML5, then it's possible that the client could be written as an HTML5 web-app, thus allowing it to be used on pretty much any smart phone (notably the Android, but the iPhone as well.) It wouldn't be a native iPhone app if it were HTML5, but it would run on any browser, including a desktop PC. But the Air Video iPhone app could still be used for iPhones, and the HTML5 web-app for other devices.
To me, that seems like it would kill two birds with one stone: an Android OS web-based client, and since it's HTML5, it could run on a standard PC as well. Video size, however, would need to be either auto-selected (preferable), or user-selectable (an option, though more code to write.)
BUT, since it would be an HTML5 web-app, the problem of how to charge for it comes up. For that, I think Voice Central's Black Swan
(an HTML5 web-app for Google Voice) is a good example.. For the "free version", it's ad-supported, or users can pay a yearly subscription to get no ads. And since there's really no way to pirate an HTML5 web-app, that's a plus as well. (And before any of you say "what about ad-blocking software, like Ad-Block in Firefox?", it can be coded to either not work if ad blocking software is active, or to show ads even if
ad blocking software is enabled, as Black Swan is.)