I'd be surprised if they haven't started leasing slots elsewhere, and as we all know, there are usually always carriers queuing up to get into LHR. I doubt they'd want to sell any, in the knowledge that it would be harder to build their LHR operation back up again in the longer term. If 5 daily flights really cannot be reinstated in the short-medium term, then selling slots would of course deliver the benefit in the form of additional capital for CX if they really needed it, and I've no doubt that GIP/LGW would be keen to get CX back if Cathay want to have a dual London airport operation as pre-covid.