In my opinion, three things are missing:
- Reputable OEMs to make phones (specially now that Nokia is gone, Microsoft desperately needs to bring along LG, Sony or convince Samsung to take WP seriously);
- Developer support. They need to make WP an appealing platform for developers in a way that compensates the lack of users when compared to Android and iOS.
- COMMITMENT FROM MICROSOFT ITSELF. Seriously, how can Microsoft hope to get OEMs and developers to take WP seriously when they, themselves, always leave Windows Phone for last. Microsoft prioritizes Android and iOS versions of their services before WP. Should anyone be surprised that the likes of Samsung don't give a rats arse about WP? Of course not. Microsoft itself doesn't give it.