The Coalition has been promising new achievements for Gears of War 4
to come with the March update. While details of the update itself are yet to be revealed, the developer had been making plans to include an old-school style Seriously achievement within the list. The details of this achievement have been finalised, and they're not what the developer originally intended.
The new achievement will be called Slaying It and will task players with reaching 5,000 kills. These kills are not retroactive as the achievement is intended to be "a new goal for players who are interested in achievements". According to Community Team member TC Octus, this is because the team received a lot of complaints about the number of previous update achievements that could be unlocked retroactively, leaving nothing for dedicated players to work towards.
The specifics of this achievement have changed since their first proposal. Originally titled Seriously Old School, the aim was for players to get 10,000 kills (also not retroactive), but with many players having already put in significant playing time since the game's release in October 2016, several thought that this was too much to expect from players in the future.
At the moment, this is the only achievement for which we have any details, although the team has previously assured players that there will be no Wings achievements or an extension of Master at Arms, nor are they currently planning any more campaign achievements. Some of the achievements will be based "around 'Knowing Your Role' in Horde", though, encouraging players to use their Horde classes properly. When we get more details on these achievements beyond teasers, as well as the update itself, we'll be sure to let you know.