Right, so it's just a new OS... but it effectively dead-ends the Lumia, making it considerably less valuable.

For that matter, who is going to buy an Android 2.3 device now, since there's no reason to believe it will run Android 4.0?

It's one thing to know your phone will eventually be obsolete, it's another thing when that eventuality is imminent.

They changed to a better kernel. A really old and battle tested kernel. It is an exceptional reason to break compatibility but it's hard to argue that they shouldn't have made the decision. Certainly they won't switch kernels again soon because there is no better Windows kernel than NT.