We don’t know when the film is going to be released, but the way TLC’s statement about it was worded somewhat implied that it was still in an early planning stage, in which case it’s going to be a while until we see it on the screen.
We also don’t know if it’s going to be a single installment or if the network is considering a longer sequence of several films with such a theme, and the latter could also make sense, although the network has enough on its plate at the moment to go for a long-term production like that right now.
They have already been rearranging their schedule after pulling “19 Kids and Counting” from the air, and it doesn’t look like the show’s cancellation has had any negative impact on the network’s success.
If anything, people have been commenting for some time that the show was due to be taken down after the allegations against Josh Duggar surfaced, but there was always a somewhat big debate about this, with some claiming that it would be an extreme measure until the charges have been proven. Which, as we said above, hasn’t happened so far and we don’t know how likely it is that it will happen in the future either.