Hi @mitozen, first of all, welcome to the Mozilla Discourse community.
I think there is a misunderstanding here, as the extensions you name actually just got it’s own API, so they can inject user scripts into websites properly.
So I doubt Mozilla will take away the special possibility they have just introduced.
So “Remotely hosted code” likely still just refers to code inside of the add-on that has elevated privileges (those of add-ons). E.g. when an add-on includes a script from the add-on author’s website. This was and likely will stay disallowed.
User scripts only have access to the current website…