While I don't know the actual practices at Ford, I would be surprised if Ford is using wifi to put software on the 2017 model year vehicles. While I expect the updated software itself that is going to go to our head-units will be the same as the '17 model year vehicles, I'm not sure if they have it ready to be deployed as a wifi update at the same time they have the software ready to be put on the 2017 model year vehicles. I suspect they flash the software to the vehicles by a more direct method.
I worked in the automotive industry for a while and I now work in the software industry so this is just an educated hunch.