I'd like to point out that SE has been very vocal about warning us when collaborations are not permanent. Even Garo was noted from the beginning, "it will be around for a long time but not forever."

And has been pointed out, Alliance raids - in this case, Nier - they are core content, not some side activity. Removing that would be rather harmful to the game. And, you know, SE owns Nier so they don't need to worry about contracts expiring.