They will likely be in the same positioning as the currant political leanings, even while teenagers are still developing their own view of the world. We hear the myth about people with left leaning maturing into conservative as they age, when the truth Iis those who develop political views at an earlier age will maintain their position through their lifetime. The question remains about the neutrals who start having children and get married. Polls have shown a certain type of Millennial that has drifted rightward are those very people I'm describing. They were not people who participated in the Occupy Wall Street protests or voted at all when they were 18-22. Political engagement was not in the veins until they started to mature and felt hostility towards the left bent of those younger than themselves. They are on the older end of Millennials(1981-1985) than the younger end of Millennials(1993-1996), who are as left leaning as Gen Z.
The idea that ideological change with age is a myth which has been debunked is itself a social media myth based off misreads of a few pieces which themselves conflated studies of partisanship with issue positions.
Historically partisanship in America has been cultural and tribal. Absent either a major realigning event to shift their social miliu or a major personal event(divorce etc) don't tend to change party. It is a major signifier both to oneself and others to change the party you support, and identifying as a swing voter itself sends signals, many not positive.
However, that disguises substantial ideological shifts. Many of those who took part in occupy wall street may still call themselves Democrats but they have very different politics in the same way Bill and Hillary got their start with McGovern but ended up in a very different place.
It would have been unthinkable socially and career-wise for the Clinton's to have left the Democratic party or contemplated doing so for one instant. However, it would have been equally career ending for them not to shift their positions on a host of issues within that partisan identification.
Colin Powell was still calling himself a Republican up until his death having not endorsed a GOP candidate for several elections.
As long as demographics remain where they are and the GOP brand what it is, GEN Z will be Democratic leaning but it is almost certain a good number of those within it will end up feeling if not embarrassed about their own behavior, determined to condemn the next set of kids for trying it. And dropping a whole lot of their ideological language and baggage.