SpaceX's IPO filing has revealed how its CEO Elon Musk could become the world's first trillionaire next month. Musk owns 5.1 billion shares in SpaceX, along with nearly 350 million stock options priced at $8.39. If SpaceX achieves a $2-trillion valuation, Musk's wealth could jump to $1.1 trillion. This would make him over 3x richer than the world's second-richest person.