Oh my god. I think I have it. iPadPro.
Apple will add OSX to the iPad.
It'll be accessible by booting into it while connected to a dock onto an external display and peripherals, and run with the screen off. Boots into iOS when it's undocked. Apps can share data between their OSX and iOS versions, so Pages for iOS works with the same file you open in Pages in OSX.
It might be extra beefy with a huge battery and super powerful chip, and thick enough for a Thunderbolt port (on a little aluminum pillar on the end?). Maybe Intel silicon if they can passively cool it, maybe a monster custom ARM design.
Think Surface Pro added size over the Surface RT. Same design, just thicker and way more powerful. Still 9.7" though.
Apple feels that touch UI is inherently different than pointer&kb, but I see the utility in something like the Surface Pro (touchscreen laptop without an attached keyboard). This is a blend of both, saying "no" to using both OS's with both inputs.
Dumb? Brilliant? Burn the heretic?