"Upgrade" will be pushed down to everyone's throats, as security patch if nothing else helps.
"Some people are tempted to turn off Windows Update completely to avoid getting the new operating system – don't. It'll leave your computer vulnerable to attack as you'll no longer get security patches."
Yes, and? How long it takes MS to "offer" windows 10 "upgrade" as a security patch?
They've already pushed it as a mandatory "patch" several times and it's obvious no brain activity will hinder the money grabbing and setting "upgrade" as a security patch is just a flip a bit: Totally trivial.
So it will happen when semi-voluntary updates stop: Only way to stop it is to stop updates, as long as you still can do it.
It's certain that in some point one patch bypasses all updating related user settings. just like W10 already does. Then it's time to push w10 upgrade again and you can't stop it.
That's the way MS is planning, obviously.