I just hope that Apple isn't EOLing the earlier models as quickly as they did with the iPad 1, given the rate of releases.
The iPad 1 came out in early 2010 and by mid 2012, they had stopped releasing updates for it, despite still supporting the iPhone 4, which has essentially the same hardware (making it technically capable of running iOS 6).
This is all well and good for phones, which tend to get replaced every 2 years or so - but on a machine designed to be a general purpose computing platform, it's quite frankly absurd - and their motives are transparent.