I’ve always thought there’s an opportunity for 3rd party monetization on customizations for Discourse. I don’t think selling plugins is feasible long-term (complex to maintain, bugs can cause show-stopping issues, hard to sell in an open-source community).
However, there could be opportunity for selling themes/components and creating a browseable place for them to live. I’d feel more comfortable pushing our userbase toward front-end customizations vs. plugins simply due to the many issues plugins can have. Our theme system has matured quite a bit in the last few years since I started working on customizing Discourse, so much so that many customizations don’t even require a plugin anymore.
Nothing’s on our roadmap in this area at this point in time, though.