Windows Phone is now officially a mature OS with all the bells and whistles you expect from your OS. It's got from Cortana, to Here Maps, to the action center it looks, feels and acts like a modern smartphone OS. However one of the ways it still lags is the App count. Microsoft has been working very hard to court developers but it's still an uphill battle since the user base isn't as large as iOS or Android.
Now there are reports that Microsoft is looking to take the "if you can't beat them join'em" approach. That Windows 10 devices will run Android apps. Would it be the all out Play Store? No they would need to place the entire suit of Google apps on the devices to gain access to the Play Store and we all know Microsoft is not doing that.
What is more likely to happen is that they will use a third party like the Amazon App store or Microsoft would even start having an Android section of app store. The real question is would this kill the native Windows Eco-System?