I don't think anyone can really answer that question in a satisfactory manner. I assume Microsoft hopes it will succeed.
I got no relations to Novell or the Mono people (just a fan of Mono), but I feel like I should mention you can actually do iPhone development in C# with MonoTouch. You can also write iPhone apps in Flash/Flex now.
I've looked at monotouch, but I'm not about to pay 250$ for a license