How long will Apple iPad Air 2 be supported by Apple?

Third party app developer support will be much longer for that iPad than from Apple.

Third party apps developers wiil, typically, support an iDevice, that Apple has ended support for, for another 2-3 years, or so.

That is just as important.

Nobody knows what Apple’s plan is for supporting devices. As we are not allowed to speculate here, I will guess instead.

The iPad Air 2, is the oldest “full size” iPad that was able to download iPadOS, so that indicates to me that it may not be eligible for the next major software update, iOS 14 or whatever it will be called. That doesn’t mean that Apple won’t release security updates for it, but I’m just guessing.