So far, Apple has been able to release iPad updates every year. They have also been able to show some serious improvements in speeds year over year. Unfortunately, they are hitting a wall in terms of processor upgrades.
Here are the history of iPads and their build process
iPad - A4 - 45nm
iPad 2- A5 - 45nm
iPad 3- A5x - 45nm with more cores
iPad 4(retina)- A6x - 32nm with more cores than A6.
iPad 5(air)- A7- 28nm
iPad 6(air 2)- A8x- 20nm
iPad 7 (air 3)- A9- 14nm process
As you can see, the Air 3 will have the A9 processor which Apple is currently ahead of schedule on. In comparison, Intel is also working on releasing their 14nm processors in early 2015 though some may be available in 2014. Intel, which is the leading processor company in the world has only been able to decrease nm build every few years.
Apple will be stuck at the 14nm process for a while. I don't believe Intel is prepared to release 8nm processors until sometime around 2020. There is a chance that Apple could build an A9x in 2016 as a follow up to the A9. But at this point it will be getting diminishing returns. We will also see less significant bumps in speed after reaching the 14nm process until reaching an 8nm process.
In my opinion, the iPad Air 2 and Air 3 will be very long longevity devices. I bet you will be able to use the Air 2 and Air 3 for at least 6 years each due the increased ram and speed capabilities.
Here are the history of iPads and their build process
iPad - A4 - 45nm
iPad 2- A5 - 45nm
iPad 3- A5x - 45nm with more cores
iPad 4(retina)- A6x - 32nm with more cores than A6.
iPad 5(air)- A7- 28nm
iPad 6(air 2)- A8x- 20nm
iPad 7 (air 3)- A9- 14nm process
As you can see, the Air 3 will have the A9 processor which Apple is currently ahead of schedule on. In comparison, Intel is also working on releasing their 14nm processors in early 2015 though some may be available in 2014. Intel, which is the leading processor company in the world has only been able to decrease nm build every few years.
Apple will be stuck at the 14nm process for a while. I don't believe Intel is prepared to release 8nm processors until sometime around 2020. There is a chance that Apple could build an A9x in 2016 as a follow up to the A9. But at this point it will be getting diminishing returns. We will also see less significant bumps in speed after reaching the 14nm process until reaching an 8nm process.
In my opinion, the iPad Air 2 and Air 3 will be very long longevity devices. I bet you will be able to use the Air 2 and Air 3 for at least 6 years each due the increased ram and speed capabilities.