Correct. You can get directed anywhere where BA wants. So you could in theory get booted off the 747 as the fleet reduces in size. That might be to SH. The 350 is going to replace the 747 on an hull for hull basis.
However, there might be enough guys bidding off the 747 to fill their requirements leaving you protected. I guess it’s a last resort thing. Some new guys were directed off the 380 a couple of years ago. If they have an oversupply of pilots on a fleet, they normally run a supplementary bid and people can put in their preference as to where they’d like to go. Happened on the 318 when they reduced the fleet to 1 aircraft a while back.