I read on another topic that before John McAfee died he called his wife to see him. there's no way he took all his crypto assets to death because it must be quite a large amount. His family must have secured all his assets before he died.
There are a few things that need to be remembered here. McAfee didn't took the decision to take his life all of a sudden. He was planning to commit suicide, if the court orders his deportation to the United States. When that is the case, I don't think that he will intentionally keep the private keys away from his wife. He might have told her how to access the wallet backups, when he met her for the last time. But now there is no way for the law enforcement authorities to prove this, unless his wife admits that she can access those coins.