Spotify and the music publishers are mutually dependent. They could crush them but they'd be torpedoing their own revenue.
>Even their current scale, the surviving music industry oligopoly could probably still crush Spotify if it tried to do jumpstart a private label.
Rather than pulling their catalogs from Spotify, it'd be smarter for them to cut better deals with Spotify's competitors so they can undercut Spotify. If the publishers have multiple, more or less equally sized number of buyers, that'd be the ideal scenario for them.