SpaceX's stock has been on a wild ride since its IPO last month. But buckle up: More big moves could be ahead.

Elon Musk's rocket company will officially join the Nasdaq-100 index tomorrow, following Nasdaq's decision to fast-track newly public megacap companies under new inclusion rules. That means index-tracking funds are gearing up for a SpaceX buying spree.

Mutual and exchange-traded funds with a collective $800 billion in assets track the Nasdaq-100, and these funds are expected to buy shares of the rocket company after today's close.

Analysts expect that could lead to a short-term boost in SpaceX's stock price. Looking further out, though, gains are far from guaranteed.

My colleague Jack Pitcher wrote a helpful explainer of what we can expect with SpaceX's inclusion this week: