It depends on the other evidence the prosecutor has. Certainly no prosecutor wants to go forward without the victim but in many cases there is enough additional evidence that the victim's presence is not an absolute necessity.
If the vic does not show up for a settlement conference nothing will happen most likely. If its set for trial, and the victim was served a subpoena - then he could face legal issues. A lot of what happens with this case depends on the alleged statement made, any possible admissions from you and the "victims" willingness to cooperate with the case. Are you facing a misdemeanor, or a felony strike?? Get an attorney's advice on how to handle this!
This all depends on several factors. First and foremost, if your husband has shown up to court and has been ordered back, he must appear or will face a bench warrant. If he has not shown up and does not show up, they may try to personally serve him with a subpoena. If he is not served with a subpoena, he will not be required to show. If he is served, he will face a bench warrant.
There are ways that he can avoid testifying and there are ways you can have the case dismissed or substantially reduced. Check out my Domestic Violence legal guide on Avvo. The same principles apply to Criminal Threats. http://www.avvo.com/legal-guides/ugc/california-domestic-battery-laws
Seth Weinstein, Esq.
Los Angeles Criminal Defense Attorney
This reply should NOT be considered a legal opinion of your case / inquiry. At this time I do not have sufficient factual/legal documentation to give a complete answer to your question and there may be more to the issues you raised then I have set out in my brief reply.