If you’re a developer, it makes sense to go with the platforms that have the most traction. You have a much larger pool of potential customers with an iOS app, than you do with a BlackBerry or Windows Phone app.
That said, it would be a mistake to bet against Windows. The pool is so huge, that even a small success on Windows can be more lucrative than a grand slam on other platforms.
So, if you haven’t already, you should take a look at developing Windows 8 apps. And, you should definitely check out the flowcharts in this post to help you determine the best possible revenue model to help you make money from your efforts.
You should also read 11 Ways to Make Money Developing Windows Store apps.