It might be the end of BA at LGW but maybe not IAG, in a scenario where Covid damage and the economy isn’t too bad this could be a good excuse to reduce costs substantially by just transferring the slots across to Vueling/Level on lower costs. The overwhelming bulk of routes are good fits for those two anyway. Remember it’s probably more likely than not Norwegian will be gone (from the UK anyway), TCX have already gone and Virgin are shaky. There is already a gap in leisure-oriented long haul and soon this could be significant.
If Covid is truly devastating it’ll be irrelevant what happens at LGW because it’ll be all about last-gasp survival mode and utilising unwanted LHR slots and capacity for anything worthwhile currently at LGW.