In Call of Duty one last Double XP Weekend will occur before the start of Warzone Season 6. Starting Friday Sept. 25 at 1 p.m. ET players will receive double XP, double weapon XP, and double battle pass tier progression. This will be the last double XP event before the launch of Warzone Season 6 on Sept. 29. so if you have been having trouble racking up those tiers for the Season 5 battle pass this might give you the chance for one last push.
Season 6 will introduce two new Operators, Farah and Nikolai, unlocked at tier 0 and tier 100 of the season 6 battle pass respectively, and will also open up an underground system of trains and tunnels under Verdansk for players to explore. It's unclear whether the train lines will be used purely as transportation or if the stations and tunnels will also be used as some Metro 2033-style, dark and claustrophobic areas for players to either hide in, or draw other players into for pvp in the dark. Based on the little info given in the trailer it is difficult to tell, however it might be a cool atmospheric choice if it is implemented that way.