No it does not, nor will it. The throttling is done on the server-side of things, so the client can't possibly know if it's next request is going to be satisfied or not. The irony is, to make
work, the client would need to communicate with the server, which would make this point completely irrelevant.
The other APIs that have server communication do not have this sort of queryable API (with the exception of the full auction house scan, which is clearly an exception), so I wouldn't anticipate getting a function of this sort.