Nokia dumped Symbian for Windows, not MeeGo (although MeeGo was also heart-broken by the announcement). If the N9 does well enough, there will certainly be more where it came from.
You had me at "I don't think Nokia's leadership thinks".
They must have known this device was in the pipeline when they made the WP7 announcement. It really doesn't seem like they gave much thought to how that would impact this (otherwise easy to get excited about) product's launch…
It's not necessarily a bad idea to take on Android and iOS as distinct challenges. Splitting resources is a necessary duty; it should be done in an appropriate way.
