Warning: SPOILERS ahead for Riverdale season 6, episode 4, "The Witching Hour(s)."
Sabrina Spellman (Kiernan Shipka) made her Riverdale debut in season 6's "The Witching Hour(s)" while seemingly confirming her resurrection following the events of Chilling Adventures of Sabrina. Shipka starred as the titular witch in the Netflix series until it was canceled ahead of the fourth installment. Though it aired on a different network from Riverdale, both series were created by Roberto Aguirre-Sacasa and existed in somewhat of the same universe based on references, Easter eggs, and crossover characters. With a Riverdale/Chilling Adventures of Sabrina crossover on fans' minds for years, the CW finally fulfilled the wish by bringing Shipka's Sabrina to Riverdale, but it came with a complicated twist.
Riverdale season 6's "The Witching Hour(s)" marked the fourth entry in the show's special "Rivervale" event. The episode primarily focused on the Blossom family during three time periods: the 1890s, 1950s, and present-day. Cheryl Blossom (Madelaine Petsch) recalled the lives of her ancestors, Abigail from the 1890s and Poppy from the 1950s, as her grandmother Nana Rose (Barbara Wallace) prepared for the afterlife. All three stories took place during the arrival of the mystical Bailey's Comet, and its power apparently helped warlock curse Abigail for eternity. In fact, Abigail, Poppy, and Cheryl were all the same person who took on new personas to hide their immortality. Since she was ready to move on beyond the curse, she called upon an old friend for help.
Not only did Riverdale confirm the Rivervale version of Cheryl was a witch, but the show claimed Petsch's character was a close friend of Sabrina Spellman. Sabrina, of course, was last seen in Chilling Adventure of Sabrina's series finale, where she died and ended up in the afterlife known as the Sweet Hereafter. Apparently, that wasn't her final fate because, according to Sabrina, witches never truly die, and she came back thanks to a transformation spell. With Sabrina's resurrection, the character was able to answer Cheryl's call to fulfill a Blossom family request: transferring Nana Rose's soul into Cheryl's body and vice versa so the original Abigail could reunite with her lover, Thomasina (Vanessa Morgan), in the afterlife. Sabrina and Cheryl were successful due to the extra power surrounding Bailey's Comet, but Sabrina's return and future in the world of Riverdale still carry a catch.
Despite the justifiable explanation to Sabrina being alive, it's important to remember that his segment in the story took place in Rivervale, not Riverdale. While Rivervale is said to share Riverdale's continuity, it's not clear to what extent. There seems to be some sort of paradox situation occurring, but either way, Sabrina still hasn't technically appeared in the primary Riverdale timeline. Granted, Sabrina's revelation about witches never fully dying means the character could still be alive in the normal universe. This line was clearly meant to retcon the controversial Chilling Adventures of Sabrina ending regarding Sabrina's fate, but it also gives hope for more appearances by Shipka in the near future.
In an interview (via The Wrap), Sabrina actress Kiernan Shipka confirmed that she never thought Sabrina "would’ve stayed dead for long." This implies there were plans to resurrect the primary character before Netflix canceled Chilling Adventures of Sabrina. Shipka also teased that Sabrina could appear in future Riverdale episodes, calling her "The Witching Hour(s)" cameo a "jumping off point." Since the universe found a way to explain Sabrina's survival, there are plenty of ways the character could reappear in the primary Riverdale focus without the Rivervale twist.
Based on the hype surrounding Shipka's return as Sabrina and introduction in Riverdale, the CW would undoubtedly welcome her return for future plots. So far, Sabrina has only interacted with a version of Cheryl, and there's plenty of interest to see Shipka come in contact with the core four–Archie, Betty, Veronica, and Jughead. Now that the door is open, it's safe to say fans haven't seen the last of Sabrina in Riverdale.