The key word is "unlikely," not "impossible." Two factors here:
1. Is he committed to change?
2. Are you willing to wait while he works on it?
My H is almost 60 and did everything he could to hide from change. But after 18 months, he finally dug in and he is doing it. It is possible. But it definitely took its toll on me.
If he is just starting IC, I'd give it a month or so, with a lot of hard questions for yourself and for him about what kind of M you would like to have. You absolutely do not owe him any kind of chance, if you are done. That is fine. You also do not have to make a decision immediately. The only thing that you need to do is concentrate on healing from this. You will be much clearer on whether you want to continue with him in a few months' time.