The initial purpose, and what Rosenstein directed Mueller to do, was to find Russian/Trump campaign ties. That was modified, and still a secret. We don't know what he's obligated to complete now. The Russian/Trump part is complete, as per the Flynn filing yesterday. Now we wait on whatever else he was tasked to complete. I think we're very close to that point, though.
Yes, I think Huber had to wait for the most part. He sat on the whistleblowers for the Clinton Foundation until recently. Why? Wray has refused to give Congress evidence based on ongoing investigations. Why would he allow Huber to out it if he won't give it to Congress? It's plausible that the additional investigations are on hold for the most part until Mueller is done.