I have a iPad Air 2 and only had it for a couple months since September last year 2015 and am very happy with it.
So I will be skipping the iPad Air 3 as I have the iPad Air 2 it is so powerful and 2GB of Ram is plenty enough and lots of apps/games are still NOT taking advantage of the power of the A8X chip and I am very very happy with the Air 2 especially with IOS 9.
And I think the iPad Air 3 won't be much of a upgrade from the iPad Air 2...
I most probably will wait for the iPad Air 4 or 5 which it will definitely be more of a upgrade then the Air 3 and that's where I think I will upgrade my iPad.
I am looking to use my iPad Air 2(bought it and have been using it since September 2015) for a least 2/3 years before I upgrade.