I would love for the creators of forum software to stop thinking about forum software quite so much, but instead to think about the goal. Which surely is to facilitate discussion. Which then begs the question, what types of discussion are there? (i.e. what are the discussion Use Cases).
Well, there are threads (topics). But that's just one. There are blog posts and comments. There are micro-blogs. There are individual messages. There are group messages. There are live chats. etc. We're not in a world now where we only communicate online via forums or e-mail.
As a website owner, you might want to host live interactive events. You might want to cover an event happening elsewhere, with others chatting in real time. e.g. a football match... you might want your site staff and your users posting media and commenting on the game as it happens (we run phpBB with a chat room add-on for this purpose).
So as an interested observer of the progress of Flarum, I'm really hoping it will become a really good 'discussion engine', and not just a traditional forum software updated with modern tech gizmos.