Today, virtually NONE of my (many) friends ever noticed something changed, until i told them.
And even with js, you can see the 'real' page popping up first before the redirect takes action. It does not feel like 'oops wikipedia is gone !!?' but more like just another anyyoing advert.
You should do a straightforward real shutdown instead, and deliver a fake 404 with explanation link. And for several more days.
And yes i would even block editing since this is also alerting people.