No, as others have said he visited Dun Eideann with Rae and they saw that the wizards there had been able to contain the incursion without it destroying the whole world. We have no idea how much damage was done in the meantime though.
OK, but that's not what people are suggesting will happen. Imagine if our guy learns to fully use his power, he severs the links that keep everyone bound to the house, creates a portal in the doorway that the residents can use to travel to their worlds etc., then why is living there with him and the other girls while they do what they want to do with their lives any less desirable than going to live somewhere else and doing it?
I suspect that what we will find is that all or most of them survived, but with no ship and no captain they separated and went their different ways. I suspect that all the girls will end up staying with him in the end (if you do their routes, at least), and narratively this means not having too much pulling them away for it to work. Having a crew and a ship wanting her back would definitely fall in that category.
Do you know where you read that? I don't remember seeing anything like that, though I only follow here and Patreon, I don't use Discord or Twitter.