This is one of the things I've been most curious about: the community is inevitably going to spawn multiple fan interpretations of classic lore and I'm certain that remake attempts of the original will, for better or worse, be a dime a dozen. If ten people make a total conversion of SC2 in the new engine, who decides the de facto standard among multiple similar mods? Community voting? Will Stardock promote certain fan-generated content if it meets a threshold of quality like Blizzard does on Battle.net or Valve does on Steam Workshop, or will the community be more self-governing and curated by the users alone? I'd imagine something will separate the wheat from the chaff, just don't know what form it will take.
Taking this line of thought further, will multiple users be able to collaborate on a single mod initiative? Using the obvious example of UQM, it involved a lot more than just one person, so assuming a team wants to tackle a big campaign style project, how will they work together most effectively to combine skills and assets into a single mod?
I know it's still early to expect firm answers but I've implored the developers to address these broader questions for how the modding community will be structured in the past and am still looking forward to hearing something more about it.