InspiredCode
16" is a pretty good size for a Wacom replacement. The 13" is a little too small. Maybe it could use Thunderbolt to really bring display lag to a minimum.
There are some rumors of macOS or macOS apps coming to iPad, maybe this would be the one? I'm sure there would be a lot of creative users that would love to run Blender, ZBrush, or other creative tools right on a larger screen iPad. If Apple wanted a killer application for Pro iPads, this would be it. It would make a lot of sense for the iPad Pro line to get more parity with Mac and allow side-loading since many of these apps would never be available otherwise.
A 16" would be nice as a desktop replacement, although I don't really like my Smart Keyboard. It makes using the iPad as an iPad too awkward. Sometimes you want to mainly use the pencil or touch, but do a little typing and that is hard with the Smart Keyboard. I would prefer a standard aluminum Apple Keyboard with a little trackpad in front like the Smart Keyboard. I'd love that for my Mac too. A Smart Keyboard with bluetooth link so it keeps working when detached might be alright too.
Hopefully a larger iPad will have at least 2 USB-C ports.
If it could run Mac apps like Blender, I would definitely be buying it.