Fabien Potencier's keynote at SymfonyCon Brussels introduces the groundbreaking Terminal component for Symfony, a major iteration built on the existing console component. This new addition, set for a multi-year development, aims to enhance Symfony's command-line interface capabilities significantly. It will include features like improved color handling, intuitive styling, and widget support for dynamic and interactive command-line applications. Fabien's presentation covers the component's architecture, showcasing how it can bring HTML and CSS-like styling to the terminal, along with support for interactivity through mouse and keyboard inputs. The Terminal component represents a significant leap in developing user-friendly and highly functional CLI applications in Symfony.