there's no telling what canon will do...the 70D had wifi before the 7DIII came out...
That's a good point (assuming you meant to say 7DII not III). It's all marketing and "product positioning." If the 7Diii is going to be aimed at the high end, i.e. pros, Canon might make the determination that wireless connectivity is more of an "amateur" feature. They could decide that pros tend to want to review and post-process their images before presenting them, so such connectivity isn't needed. Amateurs (Rebel customers), the thinking might go, are more inclined to take a snapshot and want to post it to social media immediately. For studio setups, they would have the USB connectivity they've had for years (hopefully bumped up to USB 3 or C?).
Not saying I agree, just that they could very likely decide not to include it. Personally, in the 3 years I've had my 70D, I think I've turned on the WiFi twice. It always seemed like too much of a pain to get it connected. A card reader attached to my computer is much faster and easier. I'd rather have the built-in GPS tagging of the 7Dii.