One of the interesting things you notice when using Google's new Nexus 7 tablet is the setup the Android 4.1 platform provides -- namely that the tablet's UI more closely resembles an Android smartphone layout than a traditional Android tablet layout.
With Android 4.1 (a.k.a. Jelly Bean) on the Nexus 7, the home screen exists in a vertical, portrait-style orientation. Notifications live in a pulldown shade at the top of the screen. Google's traditional tablet interface, in contrast -- the model utilized by Honeycomb and Ice Cream Sandwich -- is landscape-based, with notifications appearing in the lower-right corner of the screen.
The question, then, is whether this new approach is a Jelly Bean-wide change for tablets or something specific to the 7-inch form. I went straight to the source to get the answer.
The answer, as it turns out, is the latter: Jelly Bean will use different layouts for different tablet sizes. A Google spokesperson confirms to me that 10-inch tablets will retain their landscape orientation and bottom-right notification setup even after the 4.1 upgrade. So, yes, the way Jelly Bean looks on a tablet will depend on the tablet's size; the OS adapts itself to the device in order to deliver (what Google sees as) the optimal user experience for that particular screen size.
Now, to be clear, the 7-inch Jelly Bean tablet UI isn't merely a blown-up version of the Android smartphone interface. In Gmail on the Nexus 7, for example, you see a tablet-style setup with multiple panes in the conversation list; when viewing a message, you see a single pane if you're holding the device vertically or dual panes if you're holding it horizontally (the home screen is the only part of Android 4.1 that always stays vertical, just like it does on phones with Android 4.0). In other words, Android 4.1 on a 7-inch tablet is a hybrid sort of setup designed to play to the form's strengths.
And time out: Before you start flying the "fragmentation flag," you should know that this doesn't mean developers have to worry about supporting numerous new configurations. As long as apps are coded properly, the adjustments are handled automatically on the fly. As Android engineer Dianne Hackborn explains it:
For developers, when designing your app to scale up from its phone UI, this mostly means you should pick the break point at which any major change in your layout should occur and let the layout managers take care of all of the sizes in-between. ...
Android's density scaling was designed to be able to support arbitrary densities, by including the concept of density in all of the UI specifications of the application (bitmaps, measurements, etc) and using layout managers for final pixel-accurate placement of UI elements. ...
You don't need to supply bitmaps for every possible density; Android will scale your bitmaps (typically when they are loaded) to match the current density.
So long story short: Seven-inch tablets are a unique type of form factor, and rather than simply lumping them in with larger devices (or with smartphones), Google is creating a unique in-between category specifically for them in Android 4.1.
We can safely say, though, that the tablet-style landscape orientation with notifications in the bottom corner isn't going anywhere; it just isn't part of the picture for 7-inch devices.