They'll eventually go out of business, heavily downsize, or pivot away from being accessible to non-corporate users. We'll bemoan their loss, and a lightweight competitor will rise up a few years later that is made by a tiny team who has the huge advantage of knowing what they are building.

I am sure postman is one of those products where 90% of the common features are super easy to replicate, and the last 10% take 80% of the dev org to work on.