If you extend this chart to 2011 you will notice that the platform is more mature and most of the phones will receive ICS (my wife Galaxy S is a relatively old device and will get it).
One of the biggest points that the chart brings out is that by the time most Android phones DO get an upgrade, that upgrade is no longer current. So, while ICS might come to a lot of phones, I sincerely doubt it will happen in a timely manner. One of the biggest flaws in the Android ecosystem is the ridiculous software update cycles. Entire communities have been created to try to fill that gap (rooting & ROMs), but it's something Google needs to address directly.
Note: I have a Samsung Epic (Sprint's Galaxy S), and I've been waiting months for a promised Gingerbread update.
Motorola Milestone XT720 released June 2011 (USA: August)
Runs 2.1
No bugfixes
No updates
No upgrades
Buggy as hell. 2.2 upgrades and flash support pledged by Motorola sales/support at the time of release in the US -- later clarified that those employees had been "confused" when the mothballing was made official in late November.
Those Apple green bars look quite nice, but I'm not a fan. Maybe add some Windows phone.
The problem as I see it is that since Android is Open Source, the manufacturers don't abstract their innovations into a HAL. For example, Motorola's FM radio and HDMI support is peppered all over inside the core eclair framework. So, someone has to mix it all together again with each new release. Usually in the FOSS space, we like to believe that the effort of maintaining private forks encourages companies to contribute their efforts back to the open source project. That doesn't work here, because manufacturers like Motorola also have the viable option to simply abandon their forks. Which is even less effort.
Apple has a huge economy of scale--only four or five devices (most very similar) with relatively humongous market share per device. The personnel/device ratio obviously supports a much better customer experience than any Android device can offer (with the exception of perhaps the Android developer phones).
I can only assume Microsoft knows what they are doing and enforces abstractions and barriers that limit the scope of manufacture monkeying.