Latest IDC research shows that Android and iOS made up 96.3% of the Smartphone OS Market in 2014. While Windows Phone grew 21.6% in Q4 2014 that was 21.6% of not a lot which resulted in only 3% market share.
From a developer perspective, this reflects the type of work my clients tend to be doing. Unless a client is doing something vertical and (Android) device specific, all development now seems to be on Android and iOS. It’s more common now for Android development to be done at same time as, rather than after, iOS. I haven’t seen any clients doing Windows Phone or BlackBerry development.