I don't know the numbers but I doubt that home ownership has ever been all that common among twenty-somethings. And I fully expect that many current twenty-somethings will end up moving out of the city to get more space once they have families. That said, the interest in living in/near the urban cores of certain large cities is a relatively recent phenomenon. When I entered the tech industry in the mid-eighties, almost no one in my local cohort lived in the city (Boston/Cambridge) which indeed was still losing population and tech jobs to suburban/exurban areas.

Although Boston/Cambridge have long been quite good for food, culture, etc., I think it's fair to say that much of that sort of thing has been significantly upleveled over the past 20-30 years.