Were currently greatly enhancing the SDK functionality of StreetDeck. In addition to the scripting that now exists, you will also be able create a COM based addin and possibly even instantiate the StreetDeck COM server directly from another application. You will be able to write this addin in whatever COM language you want and will no longer have to use the StreetDeck development environment if you don't want to. A .Net example will also be provided for the addins.
Making a media manager will definitly be possible to do as an addin eventually, but may or may not be possible through scripting. In any case, then next thing that will come out is the addin interface, then we will expand the SDK to enable custom media managers.