Wait for Reviews
One of the biggest reasons to wait is to see what the Call of Duty: Infinite Warfare reviews are and to see what the Call of Duty: Infinite Warfare DLC reviews are.
Typically two of the map packs stand out as amazing to most players with a third delivering a fun game, but not to the same level. The Sabotage DLC reviews are out, but some users will want to wait for a review of the Continuum Infinite Warfare DLC 2 before dropping the cash.
If you have limited gaming dollars it makes sense to wait and see what the reception is for at least the Infinite Warfare DLC 2 maps. This will allow you to get a feel for the DLC with at least 50% of the value known before you commit your money to DLC.