The first thing to note about the “Let the Right One In” series is that it is currently only under development for the pilot. This means that Showtime is not yet giving the series a full season order, which probably depends on how the pilot turns out. While there are many factors that go into a network’s decision on whether or not a project should have the green light, some of the biggest issues are budget, test audience response, and the likelihood of profit.
As Showtime is finishing the lead role for the pilot, filming for the first episode is likely to start soon. Looking at two previous examples to guess when we might hear more about the show’s future, “The Walking Dead” spinoff “Fear The Walking Dead” got a pilot order in September 2014, before getting a two-season pickup in February 2015 (Deadline). Received a pilot order in September 2016, the Syfy series “Happy!” received an order for the full season in May 2017 before it premiered on December 7, 2017 (Deadline).
Given the timeline of these two examples and many other TV shows that have gone through the same process, we’ll probably hear more about a full season booking in early 2022 or late 2021 if we’m lucky. If Showtime decides to give the series an order throughout the season, we may see the first season premiere before the end of 2022.