As the Android OS attempts to become more unified, it's still very much so fragmented. For the everyday kind of consumer it can be very confusing; phones still running 1.6 Donut, others running 2.1 ‰clair, most running 2.2 Froyo (even new ones being released with it), and the latest (for phones at least) 2.3 Gingerbread (which is only currently available on 2 phones). I'm not even counting 3.0 Honeycomb here, because it's not designed for phones and Google won't even give the source code yet because of that.
But now lets throw an extra scenario out there. Google clearly wants Android to be on as many phones as possible, this includes entry-level and low-end smartphones. Now, clearly these phones can't possibly run the same OS and APIs as a high-end phone can, especially at the rate that technology is advancing in the mobile sector, they simply don't have the processing power needed. This is where the fragmentation would get worse. In order to suit lower-end phones with lower specs, Google would have to release an entirely separate operating system that would enable these phones to provide a positive experience for the users. At some point, their core OS that is in the public now will require hardware that some countries and users won't be able to afford, and if Google wants to more or less own in market share, they'll have to cater to these markets as well, so it would make a lot of sense that we could see 2 completely different operating systems built for smartphones specifically.
On to another point, the Honeycomb and Gingerbread unified OS, Ice Cream, may not last that long either. The screen differences between a tablet and a smartphone are too great for them to be sharing the same OS; they both require different functionality especially with how Android is presented to end-users (widgets, animations, etc.).
But what do you guys think? Will Google find a way to unify the OS and be able to ship it on completely different devices? Or do you think fragmentation will only persist as time goes on? Leave your feedback in the comments below!