Google Sneaks in Seemingly Larger 8-Inch Nexus Device on KitKat Site
The side bezels appear slightly thinner than a 2013 Nexus 7 (see our review), and while an argument could be made that it only looks that way because of the slight angle the device is being held at, the top and bottom bezels are also clearly smaller, which leads us to believe it's a different device.
Possible first look at a Nexus 8 tablet.
Another alternative is that Google Photoshopped the device's display and screwed up the proportions when doing so, but that seems unlikely. We're also skeptical that Google would show off a 2014 Nexus 7 this early, as the 2013 edition was released just three months ago.

Notice the bigger bezels on the top and bottom of the Nexus 7 shown above.
Given what we can tell about the size -- it's definitely smaller than a Nexus 10 -- it seems highly probably that Google is showing off a Nexus 8 or maybe even a Nexus 8.9 to compete with Amazon's Kindle Fire HD 8.9