Likely correct, imo, but that doesn't mean the inquiry needs to be stopped. There are already over two dozen indictments and five plea deals, so there is a there there that needs to be dealt with.
Ok, but I also suspect that once Trump is out of office there will be no criminal follow-up. There will be nothing dealt with. Such is the politics of the president. I've seen it over and over, half the country feels the president is a criminal while they are in office, as soon as they leave, folks are so happy the president is gone, they rather just forgive any trespasses.