I really don't think Forstall's deperature has something to do with executives being disappointed by the lack of renewel in iOS. I think it's just Siri, Maps and other disagreements, just like previous articles stated.
To be honoust, I think iOS is great. It does a great job being powerful yet keeping this simple for the user. That's what people love so much about iOS and that's what they'll continue to love. Maye on the iPad, a more 'challenging' GUI can be useful, but on the iPhone, iOS is great as it is, really.
The looks of iOS, by some said to be out-dated, are beautiful. It's just that maybe we've gotten used to it, but really isn't. The homescreen still looks better than any other phone. This is due to the icons, the font rendering, the dock. The apps bring a lot of color, the dock is simple yet elegant. The menu's are perfect: elegant, nice switches, very well structured, very intuitive. Windows Phone and Android are A LOT worse on this part. Also
the notifications are superb, very simple, neat, and not to forget: useful! Far better than notifications on any other devices (though I haven't checked out JB that thorougly, I admit).
iOS could be improved, but a complete overhaul? No! I love it the way it is, it is almost perfect. Just improve, don't re-do it.