It may be pretty rare for Call of Duty: World War II to release something totally new to fans. Datamining has revealed almost every single new feature of the game before its release, and that doesn't seem to be stopping. Most recently, a leak from YouTuber/Twitter user MrJaRnii has shown off some new weapons and game modes.
In a video, which has of course been taken down, MrJaRnii plays a bunch of new game modes against computer players to show them off. Some of the modes revealed are Gun Game, Infected, Demolition, and Control. There are a number of currently unavailable weapons showcased in the video as well. There's also even a Supply Drop with a look different from it's predecessors. This one is covered in frost, so perhaps it's just a new type of permanent Supply Drop or one exclusive to some kind of holiday/winter event.
If you want to take a look at MrJaRnii's gameplay video, you can thank Reddit users like xXCrankXx93, who have put the video up on mirror sites. MP1st has one version of the video embedded into their site that you can take a look at also.
Keep in mind that none of these modes and weapons have been confirmed, but look on the horizon for news from Sledgehammer Games. There's also no indication of how these new weapons and modes will be acquired. It's possible that some of them could be available for free or perhaps only has paid DLC, which would of course be “free” to Season Pass holders.