FYI, we already have a single engine that works on all platforms, written in Javascript. By the end of the summer I'm confident we'll have exporting to iOS native apps, Android native apps, Windows desktop, Mac desktop, and possibly Linux desktop, using various wrapper technologies. We're missing Flash, but I don't see the point in supporting it when we already cover HTML5. On top of that we already support Windows 8 Metro, Facebook and the Chrome Web Store. Using PhoneGap you can also get Blackberry and Windows Phone 7, but that depends on the performance of the device (which we've found isn't quite good enough for HTML5 yet), but there are improvements on the way (Playbook OS 2.1 is a lot faster apparently).
Code translation tools (converting "master" code to another language) can be brittle and difficult to maintain. I wonder how that will work out.