Was excited about my pregnancy and how I'm kind of hurt....

Me and my husband are pregnant again. This is our 8th child. I know for many that's a lot but we have always wanted a big family. We sat the kids down today and told them we are having another kid. Everyone was excited accept my two oldest. My oldest daughter (16) said "Oh boy" but that's it. My oldest son (17) let out a sigh and said "Of course you are." We asked why wasn't he excited. He rolled his eyes and said he is. Me and my husband could clearly tell he wasn't and we asked why he didn't seem excited and he blew up on me and said "How many more fucking kids til you finally feel you're mom enough?!" My husband yelled at him because we don't cuss in this house. He went to his room and said "Whatever. I don't care. I'm going to college next year so I won't know them anyway." I was emotional and started crying. That was such an out of character thing for him to say. I asked my daughter was she upset too and she said she doesn't understand why we need more and she honestly doesn't want anymore sibling. Will they change their mind once the baby gets here?