Microsoft has just announced some very interesting strategies to fill the app gap with Android and iOS. Here are some interesting points,
Windows 10 for Phones will have a Android subsystem enabling it to run ported Android apps
Android apps can be easily ported as universal Windows 10 apps. Most of Android code can be used.
iOS apps can also be ported easily as universal apps.
And a surprising revelation. Candy Crush Saga on Windows Phone is an iOS port. So, Microsoft already knows that app porting will be a hit with Windows Phone users.