Ford will delay as long as possible and she may be "unexpectedly hospitalized" if needed to delay this well past mid-terms. Hopefully, the FBI will only interview Mark Judge since he is the only one who has not made a sworn statement, and then use the Ford's Senate testimony and the other alleged witnesses sworn affidavits and call the investigation. There is no real reason why they would need to personally interview them when they are already on record.
Also, if you look carefully at Trump's wording this sounds like he ordered the FBI to do yet another background check to ensure Kav is capable of handling classified documents, rather than this solely being about the groping allegations. If that is the case, the FBI doesn't really need to talk to anyone unless they deem them relevant to his security clearance.