But why not go after these sales with WP devices themselves instead of this roundabout way?
Don't get me wrong. I'm definitely not going to argue with you about how many people the Nokia X will eventually convert to WP. I'm just as sceptical as you are.
Otherwise I pretty much agree with tgp. The Nokia X really is about the apps. Particularly in China, where Google's services aren't available. From what I understand, Chinese Android stores include thousands of apps that are specific to the Chinese market, many of which aren't even available on iOS. Given that even iOS hasn't got a grip on the Chinese app situation, I expect the WP app situation probably resembles a barren wasteland. I don't see how the Nokia X will change anything about that, but at least Nokia isn't forced to sacrifice the low end entirely.
I agree that MS is in danger of fighting on too many OS fronts. Soon they will have to deal with Symbian, Android and WP, all at the same time. Something must give. Although I see few synergies between the Nokia X and the Lumia series, I see even less with Symbian, so going with Android might be the lesser of two evils.