Is there going to be any more single player campaigns added to Battlefield 1?

While not on-hand I'm fairly certain it was mentioned somewhere that more War Stories was an interesting idea but ultimately it's not likely to happen, at least with any of the main expansions.

If we do see it chances are it'll be through a bonus update some point in 2018, but the current road plan doesn't mention it so unfortunately I wouldn't get your hopes up. Personally a War Story from the French / German point of views would be interesting to see.