From the Microsoft article:
...today, I’m excited to share how things are shaping up for entertainment in Windows 10, based on the great feedback we’ve received from our passionate Windows Insiders community.
What’s new with entertainment on Windows 10?
Let’s start with Music. Our fans asked for faster ways to access the music they love – quickly, efficiently, and on their favorite devices. And for that, we’re proud to introduce the evolution of our current Xbox Music experience, now titled Groove, with new features we think you’re going to love. Groove describes what people feel and do with music, and is more intuitive for our Windows 10 customers on what they’ll find with the app.
And along with Groove, you’ll also find Xbox Video has also been renamed to Movies & TV, making the content in the app more identifiable for our broad customer base.
For both of these apps, you’ll see the changes come through first on Windows 10 PC’s before rolling out to other devices in the coming months.
We’ve kept a keen eye on our existing entertainment fans to make sure the experiences which they enjoy and subscribe to today, will continue without any interruptions. Here’s a quick overview of the new features you’ll find with both apps in the build coming to Windows Insiders this week.
...Accessing Your Music on your favorite devices: We’re also making it easy to access your content across your favorite devices – with built-in OneDrive integration making your favorite songs only a few clicks away. Upload all your MP3’s to OneDrive, even songs purchased from iTunes, and access them all for free with the Groove app on your Windows devices, Xbox, the web — and even on your Android phones and iPhones (coming soon).
Music and the Windows Store: You can also sign up for a Groove Music Pass subscription – a premium ad-free listening experience with no interruptions. $9.99/month or $99/year gets you complete access to stream and download music from the Windows Store — one of the largest music catalogs on the planet with over 40 million tracks*. Subscribers can also create custom radio stations based on their favorite songs, albums and artists. If you already have an Xbox Music Pass (like me) – don’t worry! This will become Groove Music Pass and you don’t need to do anything.
Check out this information page for more on Groove.
Movies & TV
You will find the Movies & TV app in Windows 10 better than ever for playing all your personal videos, as well as all the movies and TV shows you love. Import your personal video collection, and play back your content in a fast and elegantly designed app that is optimized for both mouse/keyboard as well as touch. Drag and drop videos between your collections, use right clicks and hot keys for contextual menus, or go full-screen with easy to use playback controls. We’ve also added additional file format support like .MKV too.
The Windows Store: Movies & TV has direct integration with the Windows Store, where you can buy or rent from all the latest movies and TV shows in HD, as well as thousands of other favorites. Weekly new releases, access to TV shows a day after air, deals and discounts, and personalized recommendations just for you. And on Windows 10 devices, Xbox and the web, the Movies & TV app lets you start watching purchased or rented content on one device, and pick up where you left off on another device.
The rebranding makes perfect sense and is overdue - and I do wonder whether the existing applications will be renamed 'in place', i.e. as Store updates, for Windows Phone 8.1 users. There's a precedent for this with the Nokia Camera to Lumia Camera transition, and it should be smooth and easy. Perhaps the only stumbling block is that users may then be looking for the wrong application names in their Start lists. But surely that's nothing a brief explanatory email from Microsoft can't fix?
At worst case, we might have to wait for Windows 10 Mobile - but I hope it doesn't come to that: what was the point in decoupling the music and video apps from the OS if not for a case like this??