You simply cover your futures position before expiration (buy as many contracts as you'd previously sold). At the same time, you can sell your BTC for USD.

In futures markets, almost no one takes delivery, but instead they close ("cover") their positions before expiration. For example, airlines use heating oil contracts as proxies for jet fuel, because they are similar products whose prices move together. But airlines will never but heating oil on the futures markets to put in their Boeings and Airbusses.