From the Skype blog today:
Today we’re excited to release the new Skype Preview to Windows 10 Mobile with the Anniversary Update. Just like our new experience built into the desktop Windows 10 Anniversary Update, the updated Skype Preview for Windows phone has been redesigned from the ground up, taking advantage of the Universal Windows Platform to work seamlessly on your mobile device.
To get started, once you have the Windows 10 Anniversary Update on your Windows phone, select Skype Preview from your list of apps or the tile. If you have already been using Skype, the new Skype Preview should automatically replace your existing Skype app. If this hasn’t happened, you can head to the Windows Phone Store to download Skype Preview for free.
You’ll see your Skype conversation history where you can talk face-to-face on a call, message your friends in an instant to share photos, and send emoticons and Mojis to liven up your conversation.
Get together with 1 or up to 24 of your friends and family on a video call. Watch everyone’s smiles and cries when you tell them “We’re engaged!!!” To date, Skype is the only communications app that lets you make group video calls from your mobile phone—Skype lets you talk to people on phones, tablets, PCs and Macs.
Since Skype Preview is built into Windows 10, you can reply to messages directly from notifications without having to open the app via quick reply. We’ve additionally updated the UI to take advantage of the Windows 10 look and feel; however, if you prefer the light background version of Skype, go to settings and select “Light theme” under Personalization.
Although somewhat trivial, the ability to use the system's dark theme is the big win for me on the AMOLED-screened Lumia 930, 950 and 950 XL and the HP Elite X3 to come.
Ne'ersayers will say that this is just another version of Skype, but in theory this is THE one. It's a UWP app that already works on phone, tablet and PC - and will come to the Xbox very soon too.
As I said in today's podcast, the arrival of Redstone/Anniversary Update for the masses will mean that Skype could just be the tip of the iceberg. Both it and (e.g.) Maps benefit massively from the newer OS branch, but many other UWP apps will benefit from the new APIs and features. The next few weeks could be rather busy in terms of application updates!