Which icons? Because if we are talking about the home screen, that's not really where things are important. Inside an app that's using Autolayout correctly, buttons are the same size as on the Air (same pixel size, same ppi).
Of course, that's what the hypothesis is about; much like 2048 x 1536 was sacred for the iPad mini.
I think another compelling resolution for a mid-sized (9.7") iPad would be 3072 x 2304 @ 396ppi with 3X assets.
I think the rumored resolution of 3112 x 2334 makes no sense and was made up as an attempt to match the 401 ppi of the iPhone 6 plus.
Yeah, the home screen is not a good indicator of how the UI is actually being scaled (or not) on this thing. Look at something like Office or 1Password. Note how the UX elements for buttons are the same size, you just get a ton more space.
Now this is thinking along the right lines, IMO. That said, I would not expect something like that in the next year or two. The resolution this would be pushing would require hardware that not even the Pro has (yet) in terms of GPU while keeping framerate up.