What happens when Ghost gets popular enough to get their own "G Engine" competing with with Ghost (Pro)? As Wordpress.com shows, there's no serious moat for open source hosting. Either Ghost devotes resources away from their open core and towards their hosting platform, or they lose the competition for marketshare to a company that does devote those resources and then they have no funding stream, aside from what G Engine deigns to give them out of the grace of their own heart. And all of the platitudes about voting or board seats and everything else don't really make one lick of difference if you don't have any funding to make that happen, and you have to rely on pay-to-play funding from the people who are actually making money in the space, and let them set your agenda.
So, Matt's behavior aside, I do think these issues are pretty endemic to the idea of "open core" funding as a company (or market) grows beyond a certain size. Unified non-profit or dual-corporation structure (Mozilla Corporation vs Mozilla Foundation) doesn't change the fundamental logic of "where does the money come from?". I don't think Ghost is providing any new solutions here—they've just gotten lucky / been small enough to not be out-competed in their hosting niche yet.