End of an ara. I'll miss these girls, it's a shame the later volumes will never get adapted, but I get doing that is always a huge gamble.
The manga either is successful enough to keep going without any interruptions, which is ideal, or, what tends to be the more common outcome with adaptations like this, it bombs and you have to axe it prematurely by bullshitting a resolution to the ongoing arc.
By ending here they at least give you a reasonable out where most of the pressing issues are resolved, while the more avid readers who want to know more about the threads left hanging can swap to the novel.