Re-read things and found my answer:
"Moving forward, we have decided to move to a fully Composer-driven architecture and ecosystem. Each Flarum instance has a composer.json file which contains a list of the extensions to install. Composer reads this file and pulls them all in, along with their dependencies, resolving any conflicts that may occur. Everything can be updated to the latest version with a single command. And using Composer to power the extension ecosystem will enable us to deliver a Marketplace much sooner than originally planned."