Ohh…might your upcoming collection(s) be shared via an extensible system, so that others can contribute files that are accessible via the same distribution method that you’ll be using?
@tim mentioned this about 2 years ago – soon
P.s. I’m all for it containing Marketplace functionality. Plugins would be a lovely addition to such a system as well.
Associated suggestion post:
From Roadmap · Sketch FAQ: 
Is this all you’re working on? Nothing else?
We’ll try and be as open as we can here. This covers our biggest focuses and priorities, but this isn’t everything. There will be smaller things that aren’t so newsworthy and also things we have to keep a secret (who doesn’t like a surprise once in a while?). Don’t forget — we’re a small team, and we like to stay focused to get things right!
I’ve been hoping that inclusion wasn’t designed to instill a false sense of hope. A file/template/library/plugin community/marketplace would be an epic inclusion alongside Stacked Layout and nestable frames Artboards.