I know this is speculative, but I do believe that what we see on this graphic is either an elaborate internal concept or maybe even screenshots from an early build of the mobile (ARM) version of Windows 10 that Microsoft is working on and reportedly going to reveal early next year.
The image shows a combination of UI elements that we have never seen before, neither on Windows Phone, nor on Windows 8 or on Windows 10.
That UI is not exactly the same on the different mobile devices shown on the slide, it seems more like a UI that adjusts to the hardware (see navigation bar and start screen layout), which suggests that these designs are not simple graphical placeholders.
As I will show later in this post, the UI shown on these images is much more elaborately designed than a simple mockup for demonstration purposes would be.
The UI I'm talking about can bee seen on 4 of the devices depicted on the slide: A phone, a larger phone (phablet), a tablet (in portrait mode), and a convertible (in landscape mode).
So let's analyze it:
On all of those devices, there are three navigation buttons at the bottom, similar to Windows Phone (back, Start, search). On the phone and phablet, they are hardware buttons. On the tablet and convertible there is a blue navigation bar with those three buttons (software buttons) [on the convertible, you can see only a small part of the dark-blue navigation bar in the lower right corner of the screen]. Also, there is a status bar at the top of the screen, that looks very similar to the one on Windows Phone. That implies that maybe the mobile version of Windows will have the navigation bar (hardware or software) and the status bar from Windows Phone - on phones as well as on tablets/convertibles.
On all of the devices you can see that the tiles on the start screen are organized in groups with headers, and that those groups are positioned in a vertical order (plus in columns side by side on the larger screen of the convertible). That implies that maybe the mobile version of Windows will have a tile grouping feature similar to (but slightly different from) Windows 8/RT, on both phones and tablets/convertibles.
On all of those devices, there is a background image that covers the space around and between the tiles, just like it does in Windows 8 (you can see in the image that the background image on the mobile devices is the same one as on the laptop and desktop devices). That implies that maybe in the mobile version of Windows, the background image will be "behind" the tiles (not "on" the tiles) on both phones and tablets/convertibles, and that it will be synchronized across all types of devices running Windows 10.
On the tablet, the start screen is in portrait mode, on the convertible it is in landscape mode. That implies that maybe the mobile version of Windows will have a start screen that will work in both portrait mode and in landscape mode, at least on large screen devices. (In Windows Phone 8.1, it is portrait mode only)
One of the tiles on the start screens of those devices looks very much like a folder tile in Windows Phone. That implies that maybe the mobile version of Windows will have the folder feature from Windows Phone.
On the convertible, there is a group (row) of tiles that very much resemble the logos of all of the Office applications. That implies that maybe the mobile version of Windows will support a full set of Office apps (highly speculative).
Despite this being highly speculative, I think chances are high that the UI depicted in this slide is not just some mock up (a mock up for demonstration purposes would not be that elaborate), so it might actually give us some hints about what the mobile version of Windows might look like.