Bye free content, don't let the door hit you on the ass when you leave.
This is just like saying "I shouldn't leave my abusive spouse because they pay the car payment". Yea, we might (and probably not) be without free content, but the abuser will be gone.
Anyway, sites won't go away, they'll just adapt. The ads will become part of the content, or something that we've not even thought of yet.