Probably not for the iPad Pro, the touch sensitivity for that is made for the Apple Pencil, adding 3D touch is essentially useless as it kind of already has it
I see a lot of people making that excuse but it just doesn't make sense.
Pencil - Optional accessory offering precision input method for specialized tasks
3D Touch - UI element. Evolution of standard finger based commands to perform general system tasks
They're not the same at all.
The other problem would be thickness, it could come in the iPads but they will have to be a little bit thicker to support it. And you have that whole taptic engine thing... which will need to be bigger or have multiple ones working in unison.
Whats with the skepticism that an electronic device would be incapable of using two motors in sync? Not only is that an easy thing to accomplish, its not even how 3D Touch works.
The taptic engine isnt trying to wake you up from sleep. The physical response you get is supposed to a sense of immersion into the device so its not supposed to be a single unified vibration. If you're pressing an icon on the right side of a 13" tablet then why would you need a motor on the other end whirring.
3D Touch could mean thicker iPad= no buy from me.
iPad Mini Retina - Thicker for Retina Screen
iPhone 6S - Thicker for Taptic Engine
Apple TV (2015) - Thicker for lots o stuffs
Apple Siri Remote - Thicker for added functionality
Apple doesn't do it often, but if there is no workaround with current technology other than making a device .2mm thicker than they'll do it. And when technology catches up to their goals then they'll shrink it again. So for someone to claim to not buy a product with more functionality because of .2mm thickness is impractical.
No offense, but you should bookmark this thread so you can read your comments next year. You'll probably wonder what you were talking about too.