1. This effectively already exists in the form of organizations like the Apache Software Foundation.
2. Companies publishing OSS don’t usually suffer enough skepticism for them to be willing to give up control over their trademark.
3. In some jurisdictions, copyright isn’t transferrable, and only licensing is allowed [0]. The original creator always retains the copyright. You seem to be talking more about the branding/trademark, however, which is a different thing.
[0] https://en.wikipedia.org/wiki/Copyright_transfer_agreement
