I've got an Air 2 and to be honest I see no reason to upgrade it. I think Apple over did itself with the Air 2. It was the first tablet to get two gigs of ram and a Tri-Core SOC. The tablet is still pretty fast. It's also got that high quality anti-reflective coating "purple" like they have on high end designer sunglasses. In single core the A9 is obviously faster, but in multi-core the A9 vs the triple core A8x is pretty close. However, I find myself using the tablet less as the phone screens get bigger. Once Apple reduces the bezels on their phablets and gets to about 6 inches, the less relevant tablets and mini tablets become. I still know a guy who takes his ipad 2 to work and uses it with no problems. Apple built them a little too well, where it's only needed to be replaced every 5-6 years, but since mobile chips have gotten so powerful that trend looks to be gone in the near future. Just like in the 90's when a new computer would double in performance every couple of years. Not the case anymore.
Moore's law will be no more.