Nine months ago, Microsoft killed off its "Modern" Metro-style Skype app in favor of a new strategy. For desktop users, the plan was to keep the existing Win32 app. For mobile and tablet users, the plan was to create a series of decoupled Skype apps, one each for voice, messaging, and video. Those separated apps are included in Windows 10 and Windows 10 Mobile, while full functionality remains restricted to the old desktop app.
Today, Microsoft reversed course. While the naming and much of the design has changed, the company announced that it is developing a new-style Universal Windows Platform app that will run both on desktops, tablets, and phones. Unlike the old Metro app that had limited features, Microsoft's intent is that the new UWP will be a fully functional client that will one day be able to replace the Win32 desktop app.
However, the decoupled apps will remain. What Microsoft discovered is that the decoupled apps are preferred on the phone—phone usage tends to be more task-oriented, and the decoupled apps mimic the approach taken on, for example, iOS, where Phone, iMessage, and Facetime are all separate. On the desktop, by contrast, the all-in-one app fits the way people use their PCs better. The all-in-one app is more amenable to multitasking, switching back and forth between conversations and moving conversations from text to speech to video and back again.