I'm saying that even at 18 months maybe to short. Why not wait 24 months. The rumor the iPad Air 3 was delayed was 2 things. Not to hurt iPad Pro sales. The other was 3D touch for it was having production issues. Right now the only thing they can do for it without 3D touch is upgrade the processor to the same one in iPP.
They really can't add Pencil support to iPA3 since that would really hurt iPP. They could add Pencil next fall.
If they don't add 3d Touch, then all the iPA3 can get is a little thinned, smaller battery , a little lighter, A9x, 3GB ram (maybe), and faster touch ID (maybe). All this could have been done when the iPP and mine 4 were released.