You know, I always thought for a while after each child (I have 3) that I was done...no more. And then I always changed my mind (until now...I'm tired...I'm done). So my husband did get a vasectomy. It seems to me if your husband were concrete in his decision that he would have already had one. I often say extreme thoughts out loud, almost wishing I could talk myself into them, but that is not typically the case. I more do this in a way that is just venting things lying underneath the actual words. Not wanting another child really meant that I just felt like sleeping, for example. My husband has learned to take what I say as nothing more than words when I get in that mode.
Why are you worried that your husband will turn into a verbally abusive person when you tell him? Is he verbally abusive to you? If not, are you just fearful because of his response to the idea of another child (which is understandable...still, fear is just fear...it isn't neccessarily the truth).
My suggestion is you tell him in a nice way (definitely NOT through the grapevine). Maybe go out for a date night to let him know. His reaction (if he is a verbally abusive person) I imagine might be more subdued in a public setting. I, in the past, have wrapped a preganancy test in a gift with a new robe for my husband and a baby towel and washcloth for my husband and presented it on father's day. My husband has never had the dreamy, happy reaction I would love, but oh well.
Best wishes to you and congratulations...no matter what, I've learned that things in life may not go as I want or wish, but it seems that everything turns out okay anyway. (((hug)))