Few people in the upper middle class and above will use public transport instead of their car, if it's provided by their employer.
The results from the 9€ Ticket also indicate that people aren't using their car that less often. They are just using the ticket to do additional journeys [2].
But I suppose that having this ticket available for longer than 3 months will motivate some households to get rid of/ not purchase a second car. Also, it will probably convince younger adults in metropolitan areas (like me) to not buy a car - or to delay it until it's needed for family reasons.
[1]: https://www.exberliner.com/politics/red-flag-why-we-should-b... [2]: https://www.iamexpat.de/expat-info/german-expat-news/9-euro-...