I agree this data is somewhat outdated in that the Nexus 7 proves a decent Android tablet can be made so Apple's grip on the tablet market may soon loosen up a bit. It will be interesting to see how marketshare shape out for the last half of the year.
But your Microsoft argument is a bit "chicken or egg." Frankly, I think most Windows developers became such not because MS was good to them, but because it is the default computer OS. Even now they still own 85%. You go where the money is.
By that same concept devs flocked to iOS, and Android was 2nd string, not because they preferred Apple to Google, but because iOS had incredible growth and the iOS App Store made quite easy for a dev with a good idea to literally become an overnight millionaire.
I don't think Win 8 is going to be widely adopted b/c Win 8 for the PC isn't something the business world is going to quickly install. They are going to hold onto Win 7 as long as they can for stability. The tablet race is really between Google and Apple. But if Apple does come out with an lower cost 7" in the next few months, then it's really "game over." Google isn't making money on Nexus 7 so it can't lower the price further.