Regardless of your aspirations, your playing will benefit from learning as much about music as you can. By now you should have a good basic understanding of how melody and rhythm works, how beats can be subdivided and what keys are. However, many harmonica players don’t know much about chords or harmony (e.g., keyboard or rhythm guitar accompaniment).
If you have a basic understanding of these subjects you can contribute much more to band arrangements and songwriting. In fact, it is strongly recommended that you learn at least a bit of general music by taking up bass, guitar or keyboards. Ask the other musicians you play with about what they are doing and get them to show you a few things. Of course, the harmonica will still be your main instrument, but harp players who understand music are always popular and usually get lots of work.