Is it accurate to describe this as the public domain? I would expect that the bird logo still enjoys copyright protection, independent from its status as a trademark.

The core reason to enforce trademarks is not to fluff the corporation that holds it but to let the public be confident in the name. So the trademark should hold for as long as a reasonable person can be confused by the new Twitter regardless of people's dislike towards Elon.

I may be biased because I still go to Twitter via twitter.com.

Decision from the judge "Issuance of the injunction precluding Bluebird's use of the Twitter-formative marks is contingent on X Corp.'s posting of a $500,000 bond."

Both X Corp. and Bluebird have asked to go to court on Nov 2027.