TL;DR
My understanding with DCS was that it was going to be a platform for vehicle modules. There was going to be one piece of software, DCS, which would be updated when new modules were released to improve features, bugfixes etc.
In a perfect world, this DCS would have an API that allowed people to create their own vehicle modules. Or even for the developers of DCS to create their own vehicles, without breaking compatibility between modules. So you would have the DCS software, and as long as you had the external model or some sort of "compatibility" module, you would be able to see other modules that you didn't purchase online, and be able to sim along side them in multiplayer. This is the sort of direction I assumed DCS would take (before and when Black Shark came out).
Unfortunately, it appears DCS is based in some part Flanker and LOMAC code, and to refactor/rewrite that code into something mentioned above would take too much developer time. I think ED would like to do something mentioned above in the future, I'm hoping sometime after Apache DCS is done we can have this. If DCS was turned into a platform, ED could still charge 3rd party developers royalties to create modules, and have restrictions on what they can do etc. I don't really care about 3rd parties, except for the community, to be able to create new content (because every platform gets abandoned by the developer eventually, and if its a good platform, why not let the community modify or improve content for it if the developer abandons it). I would like to see DCS become a platform, and be able to buy aircraft modules and not worry about having several different DCS installs on my machine, just one DCS install with several modules. DCS should have its own code base, and the modules should be separate. If a feature is added to DCS (such as new graphics tech, more realistic instrument degradation, physics, terrain or whatever) it should be available to all DCS modules (even if the module should require an update, it should still be able to run with the new version of DCS, just without the newer features).
