In John Wick: Chapter 2, John is obligated to accept a blood oath because Santino D’Antonio (played by Riccardo Scamarcio) helped Wick leave the criminal world so he could marry his late wife Helen.
At the end of John Wick: Chapter 2, John is rendered excommunicado by Winston after killing D’Antonio on Continental grounds.
In the world of John Wick, a “marker” is a blood oath between two individuals.
Production of John Wick: Chapter 4 is still underway after its release date was delayed due to the COVID-19 pandemic.