That would depend on how far the iOS get in terms of upgrades. If you take a look at the 3GS, it's been through 4 iOS thresholds and is still a pretty strong device itself. I would say the 3GS might make the cut up until possibly 7.1 before it gets cut off if Apple decides to bring it to iOS 7. But the iPad 2 and 3 will definitely hit 7. The discontinuation of upgrades for the iPad 2 and 3 will probably be the same since their processing potential is about the same. The only reason the 3 was discontinued and the 4 was pushed in its place was really because of manufacturing and design flaws, mainly the devices exploding and catching on fire.