While the game will no longer have new updates released every month (the last was launched in late June), it looks like the next update will be made available sometime in the next few weeks. The Halo Waypoint site shows a concept for one of the new Arena maps that will be included in the update, which has a rather ancient looking art style.
Halo 5 fans can can also expect new REC items to be released, including new weapons, armors and skins. In addition, the update will contain the new Content Browser, which was first revealed in July. It will allow players to quickly find user-created content and to share them with other gamers. The Content Browser will also be a part of the upcoming free Halo 5 Forge Map Editor for Windows 10. It's likely it will be released around the same time as the Xbox One Halo 5 update.