Hi @simonstjohn,
Public collections are a very exciting feature, that we are looking forward to releasing soon. As to a timeline, unfortunately there’s no specific date set.
Right now, we are focusing on mobile apps, and streamlining our user experience across all platforms to accommodate for the mobile app changes (offline mode, realtime collab, notifications). Once this is completed Public Collections are a high priority, although they require custom collections / collection editing and improved search / filtering first.
Also please see this post about why we don’t have a set-in-stone public roadmap. I hope that helps!