Indeed, all plug-in developments were and are done in-house by Esko development teams in Prague, Gent, Shanghai and Bangalore.
The reason why it took so long to support CS6 is that the user interfaces of the plug-ins had to be re-written because Adobe discontinued support for the ADM (Adobe Dialog Manager) UI framework in CS6 and we had underestimated the time it would take to re-implement the user interfaces on top of an alternative 3rd party UI framework. No excuse though, we were much too late and will work to avoid such long delays in the future.