Whilst a lot of information about Black Ops 3 has been released officially, there is still a lot that Treyarch are waiting to reveal. Luckily, some details have already leaked, including details about the different DLC packs that will be in Black Ops 3.
Black Ops 3 will have 4 different DLC packs, all of which will be part of the season pass. As usual, the season pass can be purchased up front and will cost considerably less than it would to purchase each of the DLC packs separately as they are released.
Unfortunately we do not have details about what content will be in the Black Ops 3 DLC packs, although it could be possible that not even Treyarch are 100% sure at this point. Considering the full game hasn't even gone gold yet, it would make sense that DLC plans are not completely confirmed at this point.
If previous Call of Duty games are anything to go by, we can expect new maps from the DLC packs, along with new weapons and maybe some extra gun camos. There may be more customization options bundled into the DLC packs. Advanced Warfare also introduced a part-by-part zombies campaign that was split up into each DLC pack, and this may be the same for Black Ops 3.
Hopefully the standard zombies mode will be available alongside the base of the game, otherwise I think a lot of Call of Duty players will be very unhappy about Black Ops 3.