I am not an expert, but my thoughts: I could see them bringing new features in that might take more horsepower. I don't think it will happen so quickly that they would kill off everything pre 3rd gen. I mean, iPadOS is support back to the Air 2 which is a late 2014, coming up on 5 years of support. 6, if you count up to WWDC 2020 which would be the next chance to hear it gets dropped. Apply that same timeframe to the Pros, and your perspective device that is nearly 2 years old, and yeah you meet your desired lifespan. I do think it is possible or even probable that some future features are not supported on older models. There are better deals out there if you are SLICK