Lol, poor iPad 3 (A5X/1GB).Well, there are 2GB devices sporting the A8, A9, A10, and even A11 chips. I doubt we’ll see them all lose support at the same time.
Even with 1GB, there are A6, A7, and A8 devices. The only ones not still supported are the A6. The A7 will probably not get iOS 12 this year, then the A8s go next year, and so on.
That said, yep, A7 is still supported albeit unlikely to get iOS 12. That puts the iPad 4 and iPad Air (both 1GB RAM) on even footing as far as functional lifespan is concerned.