You're spot on - I have trouble believing that they're really going to put in all the effort to build an entire OS when they could achieve exactly the same end

You're spot on - I have trouble believing that they're really going to put in all the effort to build an entire OS when they could achieve exactly the same end result by merely finishing their freaking Android app. Thus far, Facebook hasn't even proven that they can competently develop a mobile app, let alone an operating system. Even if the issue isn't talent, but resource allocation, are we really to expect that they're motivated enough to develop a mobile OS if the mobile experience hasn't been important enough to them until now to even finish their app?