Next batch of Long hauls ex LHR to start to be announced shortly so we'll soon see.
When you have access to BA upper management and route planning about what is and what isn't slot sitters then you can afford to more definite.
Bit condescending that wasn't it? (and I should know!)
The situation on what is and isn't going to stay is fluid, some will perform well, some not so. It's worth bearing in mind the new long haul arrivals will be used to replace very old B767 / B744s that are on their last legs. Any expansion will be, let's say "modest." Recent forays to ICN and HND have hardly set the heather alight and Chengdu is proving an incredibly slow burner.