IOS is becoming a giant mess also - regular 4/4S phones in one resolution - the iPad in another. A future 7" iPad, the iPhone 4Stretch, The Nano and maybe AppleTV... different resolutions and with different specs.
well considering 3 of those don't exist (yet, if ever), let's look at it from an apple prospective, those older phones are due for extinction, and up until now sported the same aspect ratio, converting an app from the 3GS-4 was mostly updating the graphics in the app, so that's really a minimal transition in the world of UI development.
now, between the iPad and iPhone's aspect ratios being different, they are 2 different devices with different targets. that's acceptable fragmentation (it's not even really fragmentation).
let's think about your 3 devices that don't exist yet.
the iPad mini... if this device is released it has a 99.9% probability of having the same aspect ratio as the normal iPad, and most likely have some for of scaling down like the iPad scales up iPhone apps.
iPhone mini.... just not going to happen, everyone is wanting a bigger iPhone no one is wanting a smaller screen, and if they by chance do make an iPhone mini it' will most likely go the way of the iPod Nano and have only locked in apps and nothing more.
AppleTV... same situation as the iPad/iPhone acceptable fragmentation, it's a different device with a different target. Also know that the iPhone is going to a 16:9 landscape aspect ratio, devs can now utilize the same UI formatting for apps.
so let me reiterate, after the iPhone(5) is released there will be 3 aspect ratios (iPhone4s, iPad, iPhone5/appleTV) and now realize that the pre-iPhone5 aspect ratio is set now to die out, in estimate, in 2-3 years the 4S will be on it's last iOS update.