Alcom's rights were always going to expire, and no one had ever hinted that there was going to be a renewal, AFAIK. This is a necessary step, but not a surprising one.

I do wonder if it is something where the off-camera creatives could come back to spin the final three seasons of The Expanse up and then segue into The Captive's War. Not that they're the same setting (we assume), but we at least know there are people who can do a well-liked adaptation of JSAC books.