Although I would've loved to see them complete the entire story I was still pretty satisfied with how they left it (other than the edits they made for Alex's story).
The Expanse could always be picked back up if Amazon would get it’s head out of its ass. It stopped where the books do a time jump forward and the characters are older.
It didn’t got cancelled to be fair. It was a great show that run much longer than it’s viewership can support, and it was announced way earlier that the story will be wrapped by 6th season.
It did get cancelled. Twice. The show ended roughly where the 6th book ended and was intended to complete the last 3 books, but because it was cancelled, we didn't get to see how they would have handled those books without the time jump.
I think the most we might get is a movie. But it would be wild if in ten years or so they actually got the cast back and continued the story like in the books