Agatha All Along's ending sets up Agatha Harkness' and Wiccan's future in the MCU in a big way, and it seems almost certain they'll return.
In the final moments of the finale, Agatha – now in ghost form – becomes something of a mentor figure to Billy, after persuading him not to kill her. Instead, she suggests, it's high time they go and find Billy's mysterious twin Tommy, who has just been brought back to life somewhere in the world.
