I can’t omagine BA going back on Colombo yet again. It’s not that long since they pulled the most recent effort.
A Dubai move would not be surprising which may allow the third Heathrow frequency to be redeployed to Islamabad given the ongoing rumours about a return. I doubt that ISB would be a Gatwick route although do recall the old LGW-MAN-ISB routing with the BCal 747s...