The ghost Agatha could return in the future projects ... she can also play a crucial role in The Young Avengers after she teams up with Wanda’s son, Wiccan in the finale of Agatha All Along.

This was the first time a ghost has ever appeared in the MCU ... After losing her powers due to Wanda Maximoff's spell, Agatha Harkness encounters a mysterious goth teen who helps her escape ...

Indeed, I'm going to need Agatha and Wanda to share at least one more scene together in the future. There's a ton of bad blood between the two witches, but Agatha's care for Billy might change things.