Yes, but that's assuming that they publish the text as Twain wrote it. If they editorialize it enough they'll have produced an original work on top of Twain's w

Yes, but that's assuming that they publish the text as Twain wrote it. If they editorialize it enough they'll have produced an original work on top of Twain's work. That'll carry their copyright, and since they keep the original under wraps there won't be a public domain version of it until the copyright of the edition now being published expires, or someone leaks the original.