He will testify. He needs to find safety and protection for his family FIRST, they are in danger. He needs to seek this protection from Congress.
Once his family is secured, and if he lives long enough. He will Testify. JMO
You are pretty close. For me the key to Petraeus testimony is this.
If he turns up dead, then it was known that he was going to spill the beans.
If he lives to testify then nothing worthwhile will come out of it.