If the iPad Air 3 is to be a reality this year it has to have minor upgrades that can literally be slipped in place with relatively minor engineering challenges. Apple marketing then has to try and sell the upgrade as significant but also minor -- something only they can do.
- A better CPU (A9) = easy. Not sure if the A8 and A9 pinout is the same but if Apple controls everything it shouldn't be that difficult to sort out. Note: Not the A9X, which is a whole different beast and is the iPad Pro exclusive.
- 3GB or RAM = nope, that would require a significantly updated mainboard and perhaps the same kind of new memory controller found in the iPad Pro. 2GB is easily enough for the Air. Remember that iOS is designed to run on devices with 1GB.
- 2nd gen touch ID = easy.
- 3D Touch = nope, would require complete reengineering of the device. Apple's too busy doing other things.
- Maybe some kind of boosted Wi-Fi or Bluetooth? Easy. I'm not sure what's new in these areas, though.
One thing to note here is that Apple might still be dithering on this decision, waiting to see what demand is like for the iPad Pro and
also to see what manufacturing challenges arise from its production. If it turns out there's capacity for an updated Air, they might go ahead and do it. (I should add that some of these questions might already be answered by now but they weren't answered sufficiently for the launch event this week.)
We know from stories in the Isaac book that Apple can turn on a pinhead when it comes to manufacturing. Literally overnight they can switch materials and technologies.
Whatever the case, you'd be the world's biggest idiot if you bought an Air right now. Don't order until 1st Nov, at the earliest. You'll be getting a great tablet no matter what, but you might be getting a slightly faster tablet if the Air 3 does indeed come to fruition.