As promised, a Gears of War 4 Double XP Weekend has gone live following its earlier downtime. According to the announcement, players can earn the double XP in “any Versus or Horde playlist, plus Private Horde.”
https://twitter.com/GearsofWar/status/822514190011109376/photo/1
However, the dates mentioned in the tweet and image seem like they may be a mistake. Despite just going live about half an hour ago, the image claims the event started on the 19th, which was Thursday, and only goes until the 21st, which is Saturday. The original promise of the Double XP Weekend stated it would be live from January 20th to January 22nd, so hopefully those are the correct dates, as a one day event would be a disappointment to many players.