The release of the Nexus 7 brought a new phone/tablet hybrid UI to Android tablets. And today, most people agree that it works well - on the 7-inch form factor, anyway. The latest leaks from the upcoming Nexus 10 suggest that Google will keep using that same hybrid UI, despite having a display that's a few inches bigger in each direction.
As David correctly pointed out, the result is that the phone and tablet UIs are now virtually identical. This makes it easier for the average Joe to understand it as well as his Android phone. (Or, you know, it would... if manufacturers didn't still overwhelmingly use capacitive buttons rather than on-screen and didn't shoot the UI to poop by using custom UIs.)
As Jeremiah noted, there's an obvious downside here, though. 10" tablets are entirely different ballgame than 7". Most people hold their 10" tablet with two hands and operate it with their thumbs (and use landscape much more often), whereas 7" tablets can be held with one hand and operated with the other. Thus, it made sense that the UI was aligned along the sides on the Nexus 7.
The simplest solution is to add a toggle - but let 's be honest, Google probably isn't going to include that option for fear of confusing users when the menus already seem endless in comparison to iOS. And yes, we're going based on leaked, pre-release renders, and maybe it just looks like this because it's not finished yet. Still, it seems unlikely that the layout will change from what we've seen in the leaks.
Which UI do you like more - the old tablet interface, or the new hybrid?