Terry Myerson, the VP of Operating Systems at Microsoft, said that this unification will allow both apps stores to work as one, but did not go into detail on how users would be able to use different apps on different sized hardware.
The design of an app for the Windows 8 store and Windows Phone store is quite similar, making porting from one OS to another pretty easy. We believe Microsoft will allow users to download apps on Windows RT tablets that work on Windows Phone devices.
This would be similar to how iPad users can download scaled up iPhone apps, although Apple has pushed for more iPad specific apps in the past few years, with developers using the extra real estate to their advantage when displaying more content.
Microsoft could also go down the route of making it much easier to develop three apps for three operating systems, but this would take away the unique design, making all three apps seem like they were made for one size device. This may not be the best when trying to sell the Windows RT tablet to customers, showing all apps look like they were made for Windows Phone.
We expect this unified app store to be released sometime in Spring 2014 alongside a slew of new updates to the Windows ecosystem. With all the management change-ups and redesigns, this looks like just another move to make every platform the same.
The last few updates have not been met with incredibly warm reception, with the Xbox One on a loop since it was revealed this summer and Windows 8 not getting a lot of users compared to Windows 7. Microsoft is still trying to change the ecosystem and building a similar platform for all their different operating systems, but it is a long challenge before they get it right.