Wait for More Details
We already know quite a bit about the upcoming Battlefield 1 DLC expansions but we don't know everything. Not even close.
Each DLC expansion pack will deliver new items and maps but, as of right now, we don't know what each will bring exactly. They Shall Not Pass is loaded with new items and maps but each expansion pack will bring different content.
EA DICE typically takes its time confirming these details. For instance, with Star Wars Battlefront, the company outlined many of these details just a few weeks out from launch. And in some cases, after the release date itself.
If you're worried about paying for something you might not like or use, you should hold off until you know more about what is coming in Battlefield 1's DLC.