I'd have thought BA would be the most likely of the two to pull out, given that (a) BD will take some - if not most - of BA's Club traffic and (b) BA's future in LGW is probably not that secure; they'll probably blame BD for what they intended to do anyway. Not that one can have much sympathy; they could have avoided this if they had left JER with even two dailies to LHR.
If BE does abandon LGW, then there is another carrier that can fill that gap pretty easily ...