Nowadays the situation is completely different. Apple had showed that their vision of smartphone is successful: Microsoft (or Google) don't need to prove that anymore. Also carriers have lost a bit of their power, and are more afraid of ending up with a world controlled by one company than before.
The point of the exclusivity is that if it runs out in a few months as many expect, that's pretty much when the new MS phones will come out (give or take a couple of months). So I don't see what damage Apple made.