One thought on entry into service dates for the 777X - how reliable are they? Aside from the technical issues on the project, and strain on engineering capacity that Boeing may be experiencing, how much of the schedule assumed a fairly straightforward regulatory process? It's not hard to imagine that any regulator is going to take a much closer look now at this and any new aircraft (from either side) in the wake of the Max. If a common type rating is proposed (not sure with the 777X) then you'd expect even more time to be taken over it.
From a BA perspective it might not matter. They've demonstrated how much they are able to get life out of aircraft, but if it were me I'd be extra wary of any delivery timetable right now.