With the Divergent series,the first few installments in the franchise did better than average results, but the last film was the worst one so far. Allegiant lost about half of its US audience between it and the previous film. Granted, the film did open one week before Batman v Superman in March.
Lionsgate is still planning making Ascendant as a TV movie rather than a full theatrical released film. This made for tv film would act as the pilot for a new Divergent TV series as well. The only problem is it’s unlikely they’d get any of the originbal cast members back for it, which leads into another set of issues fans wouldn’t care for.
If I was Lionsgate I would make the last movie as a normal film and ad in specific characters that would be later introduced in the tv series. That I think would be the smart play here.