I'm not sure about this Superdesk, or if I like it, but I think that you're underestimating the number of small papers, nonprofits, magazines, political groups, and trade press outlets that are desperate for something that isn't garbage. Drupal, Joomla, Wordpress, or some monstrosity that some contractor conned them into laying off staff to afford have them on the verge of suicide, and their workflow consists of "the shared drive."

Large papers in the US are represented by about four companies, and the Tribune companies are clearly sharing a CMS. They're really irrelevant to the general market for CMSes.