If you're a Windows Insider and your device is on the Fast ring, there's an update for the Movies & TV app that's waiting for you. The version number is the same as the latest Groove update, which is 10.16112.1015.
The Feedback Hub post explicitly says that this update is for Fast ring PCs only, but that's not accurate at all. We've installed version 10.16112.1015 on a Fast ring phone, as well as an Xbox One that's on the new Xbox Insider Program.
Here's the changelog:
It's now easier to sync video you've purchased in the Movies & TV app across your devices with the introduction of your video cloud collection.
When there is a UHD version of a video in our catalog, you'll be prompted to purchase or rent the UHD version by default.
You can now purchase and rent UHD videos inside the Movies & TV app.
On Xbox One consoles, you can see how much of a movie you’ve already watched from your Homepage.
Of course, the last item in the release notes points to the Xbox One console, which would be very strange indeed for an update that was only available for PCs. Of course, only the top item could apply to Windows 10 Mobile, as there are no UHD Windows phones.
This could be considered the December update, as the last one that Insiders got was at the beginning of November. If you're not on the Insider Program, no worries, as you'll likely see these features within a few weeks.
Update: Microsoft has removed the Xbox One item from the changelog, as the Xbox changelog accidentally got posted to the Feedback Hub.