We recently learned that Square's (NYSE: SQ) Cash App surpassed Venmo in total downloads for the first time ever, and Square's stock price quickly soared to a new record high. And I believe the high share price is well justified.Although the Square Cash App isn't a huge revenue driver for the company right now and might never grow into a game-changing profit machine itself, it could represent a multibillion-dollar opportunity for Square in other ways.