I don't think so. Sometimes nouns can be omitted and implied (next=next X) but adjective still remain pure adjective. The difference with substantive is that "what next exactly" absolutely depends on the exact context and situation only. While "рабочий" as noun is always "worker".
"next" still remain a property of some object, not its definition.
You can add a noun after that adjective "next please" = "next person, please" and it is OK. If you can't do it naturally - there is a substantive.
It is easy to check - in vocabulary.