"Sleepy Hollow" season 3 ended with a shocking twist as the Witness, Abbie Mills (Nicole Beharie), sacrificed herself in order to stop The Hidden One. However, this leaves main protagonist Ichabod Crane (Tom Mison) without a guide and a report from Ecumenical News suggests that Ezra (James McDaniel) may fill that role.
According to the report, it is likely that Ezra will step in to continue guiding Ichabod in the modern day now that Abbie is gone. During the finale episode of season 3 Ezra also confirmed that there were other Witnesses out there and that they all shared the same bloodline as Abbie, hinting that he may be the one to introduce Ichabod to his new partner.
The report points out that Ezra already knows too much regarding the supernatural world and this knowledge and experience may prove useful for Ichabod as he continues his duties to stop supernatural evil from destroying the world.
However, it is undetermined how long Ezra would be in this position as a new Witness would later fill in the same shoes as Ezra. It is for this reason that some fans speculate that the new Witness that will be introduced in season 4 may be a novice and that the roles will be reversed, with Ichabod now as a mentor to a new Witness.
It is further speculated that Ezra already has a Witness in mind and that it may be Abbie's sister, Jenny (Lyndie Greenwood). Jenny would have full knowledge of how the Witnesses work and what their responsibilities are. She is also speculated to have a strong connection with the Organization and is a likely candidate for Ichabod's line of work.
"Sleepy Hollow" has not yet been officially renewed for a fourth season but if it does then it is likely the season will follow Ichabod's hunt for a new Witness, as stated by the Hollywood Reporter.