The proposed rent control in Berlin is sticky, in that the rentier cannot increase rent between renters beyond a certain amount.
The most likely scenario is that they will find a place to move into in a year or so, which will fit their family planning.
Otherwise, if they have enough for a modest downpayment as the collapse of the renting market leads to increased supply in bought housing, they can also buy a condo.
If even that doesn't happen, they can also go into public housing.
I live in a rent controlled city. The scenario you are describing doesn't happen. When I was a kid, we moved 7 times. All we had to do was look for housing a few months in advance, and move as our lease was up.
I've also lived in rent controlled cities (like SF), and my experience runs counter to yours. Your experience is an anecdote, not data.
I get the impression you didn't actually read the article. It points out very clearly that when apartments go vacant in Berlin, they're being sold, not re-rented. If that's what happens when a renter leaves, then there's no stock for new renters to move into.
And just throwing in public housing as though it's a magical solution is wildly unrealistic, especially when you're dealing with large numbers of people.
I'm sure you live somewhere nice, but it's not reflective of the world.
If the apartments are being sold, then they must find buyers. If there is no way to rent them, then it's not profitable to hold on to them, and their value decreases. At that point, people can simply buy apartments, and everyone is happy.
My experience is typical and backed by data. In my city, roughly 25% of the renting population moves every year.
The most likely scenario is that they will find a place to move into in a year or so, which will fit their family planning.
Otherwise, if they have enough for a modest downpayment as the collapse of the renting market leads to increased supply in bought housing, they can also buy a condo.
If even that doesn't happen, they can also go into public housing.
I live in a rent controlled city. The scenario you are describing doesn't happen. When I was a kid, we moved 7 times. All we had to do was look for housing a few months in advance, and move as our lease was up.