Makes me wonder.

Say 5% of the free tier users converts to a paying customer within 5 years. And user growth is constant. Then over time, you will get a much larger free tier user base, compared to your paying customers (in absolute numbers). At some point, it must become tempting to charge all free tier users a little bit to continue, because the group got so big, so there is a lot that can be earned there.

Is this wrong, or should we expect this?

Cloudflare still operates like this.