Not a legal eagle...but the Feds will not take a position so long as there is a criminal case pending. They won't jeopardize due process.
They will also wait to see what action the state bar -- and the state -- might take. They have primary jurisdiction.
At some point, though, the case will be dropped. And if Nifong's ass isn't put through a legal wringer by all concerned, it will be a gross miscarriage of justice.
The feds don't have to take a position in the case just to investigate, and they usually don't announce when they're doing an investigation, so it's hard to know.
Maybe we'll get clarification on whether it really was the FBI or if the report is wrong and it should have stated SBI.