Blizzard doesn't think this quest is going to be here every week. Alliance participation is increasing and Horde participation is decreasing. The quest will only be offered when there's a large population disparity.
At the start of BFA, the population between Alliance and Horde was about equal. However, there were some phasing issues that lead to more Horde in a phase. Then they saw the trend of more Horde turning it ON, but Alliance turning it off.
However, they think that the Item Level 400 piece might be too high. When this was added, it was months into Uldir, but now most people haven't even stepped into the new raid and are getting Heroic pieces. They're thinking starting next week, it'll be a 385 with another bonus like Conquest points instead.