BA has said today that they do not plan to cancel any flights during the strike period.
They may be correct. Let's hope they are, then no customer will be disrupted. A good outcome for all.
In the meantime, BA can't be certain which of it's crew will turn up for work/call in sick etc. Contingency plans will have to be put in place, which will undoubtedly cost money, even if they are not used.