You'd think three out of four would move out of the house soon enough, with the remaining one running her own family there. The blond one is as good as gone anyway, she had no troubles living in the USA, so she would be the first one to get out to live however she wants, wherever she wants. Natsuna might as well move into some small apartment/dorm when going to the uni. I could perhaps see Fuyuno sticking around for a little while, being the youngest, even helping Haruko. But in the end it seems to me Haruko would be the one to raise her new family in that particular house.