A common theme is friendship. Their relationship is often explored in depth, showing how they rely on each other. For example, in many fanfics, mob looks up to reigen for guidance.
Hard to say. Maybe it will if there's enough demand and the story has more to tell. But sometimes, even popular mangas come to an end. We'll just have to wait and see.
Mob Psycho manga has indeed finished. It wrapped up with a satisfying conclusion for fans. The author completed the narrative and tied up all the loose ends.