Not sure why you want to emulate XML namespaces in JSON, but JSON schemas can include other JSON schemas and extend upon other JSON schemas. That accounts for 99.9% of the use cases for namespaces.
That's my point though – it doesn't have anything to describe metadata, so therefor trying to cram in additional semantics is futile if you still want to call it JSON. Call it something else and you can attach whatever semantics you'd like, but they think it should be served up as `application/json` which means all those semantics go out the window.
http://json-schema.org/
Not sure why you want to emulate XML namespaces in JSON, but JSON schemas can include other JSON schemas and extend upon other JSON schemas. That accounts for 99.9% of the use cases for namespaces.