Warning: spoilers ahead for Insidious: The Last Key! Read ahead at your own risk!
From the very beginning, Insidious' Elise Rainier (Lin Shaye) helped carve out the franchise's identity. A strong and capable medium with a secure connection to the franchise's trademark realm, The Further, she has stood as a central focus of the series as it has moved into its most recent sequel/prequel, Insidious: The Last Key. However, The Last Key does far more than just offer up a look into Elise's childhood; it also provides us with a potential new heroine in the form of Imogen Rainier (Caitlin Gerard) and offers up a path for the Insidious brand to move forward indefinitely.
Most Insidious fans likely already know that canonically speaking, Elise Rainier has a particular endpoint on the franchise timeline. She dies in Insidious Chapter 2, which means the two subsequent sequels take place before the events of the first film. A dead Elise inherently implies that the Insidious franchise can only use her in stories that take place before Insidious Chapter 2 (which is exactly what the studio did with Insidious Chapter 3 and Insidious: The Last Key), but handing off the franchise to Imogen Rainier would drastically open up the timeline and allows the series to produce new sequels unhindered by story constraints.
Narratively speaking, handing down the franchise from Elise to Imogen also opens up many new opportunities to keep things fresh. Imogen is still learning how to use her abilities to explore the intricacies of The Further, which puts her in a position closer to a hero origin story than the seasoned, experienced status of Elise. By shifting focus, a hypothetical Insidious 5 could offer audiences a hero who is far less self-assured in her exploration of the paranormal, and that's an arc that could realistically continue for several films.
Beyond that, there's merely a matter of longevity to consider. At 29 years old, Caitlin Gerard could conceivably stay in the series far longer than the 74-year-old Lin Shaye. Make no mistake, Shaye is still fully capable of playing Elise from a physical standpoint, but Imogen has decades of stories ahead of her, and Gerard is young enough to take her character in a far more visceral and physical direction.
Having said all of that, the presence of another medium in the Rainier family doesn't inherently guarantee that we will get more spinoffs and sequels in the style of The Conjuring universe. Introducing Imogen and her own psychic abilities help provide some context into the nature of Elise's skills, but there's nothing to indicate that the folks at Blumhouse and Universal have concrete plans actually to make Imogen the new focus of the franchise. However, her very presence in this universe means that it's now possible, and I think it could be the perfect way to move the franchise forward.
Only time will tell if Imogen Rainier will eventually take the reins and become the new heroine of the Insidious franchise. Until we learn more about the future of this horror series, you can still catch Insidious: The Last Key in theaters now. Of course, if you have already seen the most recent installment in the Insidious franchise and are looking for even more thrills this year, then you can check out our guide on 2018 horror films to watch out for, as well as our 2018 movie premiere guide to get more information on everything debuting in theaters this year.