Is that really the only thing that you want from the new iPad Pro? I've got an iPad Air 2 and there is more than enough performance for everyday tasks. Right now, you won't see any difference if Apple adds another 2GB to the 9.7 iPad Pro. 12.9 iPad Pro only has 4GB because it has a much higher resolution screen.
Yes, but apple could require 4gb for a more pro ios/PadOS for better and new multitasking, etc functions. And that is what WWDC will mean for the ipad, they' ll show a more complex IOS with more functions for the ipad pro(with 4gb), and that is why apple is not in a hurry to update the 12.9, it already has 4gb, and the rumored 10.5 will also have 4gb.
They want new hw to show this ios pro/PadOS on, and showing it on the 1.7 years old 12.9 inch ipad won' t have that effect/feeling of domething completely new.
So my guess for the line-up:
Ipad 9.7 without pencil/smart connector
Ipad 9.7 " pro" is on its way out in a year, but has some pro functions , like the pencil and smart connector/keyboard
Ipad 10.5 and ipad 12.9(current en new) will have some extra "pro" functions with ios 11.
(Filemanager? Higher res, multi account?, even a smart keyboard with a trackpad?)