It all depends on whether Windows 8 will be a hit. At the IFA, so many Win8 devices are showing that I fear consumers will simply lose interest because they all start to look alike. Over the past few days, I can't even remember how many Win 8 tablets with clip-on keyboards I'v seen. With so many variations, it's hard to get excited about a single one, unlike the iPad of which there is only one (alright, tow, if you include the older model).
If consumers feel that Windows on a tablet is a good idea, and the concept takes off, then Nokia might be able to hitch their wagon to this upsurge.
Your statement that "A market leader can rapidly lose the affections of the public" might be true, but I hardly expect Apple to lose their 'cool' appeal; they've been doing it for over ten years now. Unlike many of their competitors, they actually seem to have a plan, and follow through on it. Dell and HP are just reactionary, always have been. Samsung couldn't design themselves out of a wet, white with fruity logo paper bag, and why should they?
Nokia's strength has always been based on a different model: sell a lot of cheap phones. Even their advanced gear was predicated on a solid bottom line based on dumb-phones, despite their bragging about having had an iPad and iPhone in their labs for years. If they relied on cutting edge tech, then they would have released it.
The game is being played now in an area where Nokia has very little expertise: computing. Microsoft wants to get in on this game, and they need Nokia right now because no-one else will touch them with a 10 foot S-Pen (please don't speak if you're going to mention the new WinPho8 Samsung models).
So what is Nokia to do? Frankly, in terms of software they're shackled to a company that has always been slow to react. In the past that was never a problem, but Apple and Google are moving so quickly now they need to be very focussed in order to catch up, and I don't see Microsoft doing just that.
On the other hand, if Win8 turns out to be a bit of a Vista, it's bon voyage and walk the plank for Mr. Ballmer. This will lead to a leadership crisis within MS. Sinofsky will most likely take over, but apart from continuing guaranteed cash cows, what exactly has he done? So, if they shop around for a new CEO it will take at least six months (maybe they should hire Elop, that would be a coup...), and even then the strategy will change. Which is a long way of saying, if Win8 fails, Nokia can loof forward to another year of nothing with regards to WinPho.
If I were in charge of Nokia, I'd say "fuck it" and build lots and lots and lots of small devices that all communicate together. Make the smartphone obsolete. Do deals with every large public service company in Europe and Asia (screw the Americans). Small camera's for your home, gardering tools (register Ph values, humidity &c), build an army of small devices people can throw at anything for next to no money. That's the model that made Nokia big, and as far as I can see it's the only model that will help them get back to their former glory.
Anyway, that's just the way I see and I'm sure the real picture is completely different, I just thought I'd vent my two cents.