Skipness the 767s have to be off the North Atlantic by 2015 due to requiring an avionics upgrade. They'll continue to serve Africa/India etc
Wasn't the B77Ws a special deal for British Airways because of the 787 delays? Quite a few of them are not even owned by BA itself, and are leased. I don't know who by though.
Quite a few factors I've heard regarding the Sydney route, which was almost pulled but BA moved the 77W onto it (Good Cargo Capacity) and better economics than the 747 for that distance. Also it was changed to Mixed Fleet CC.
I've heard a rumour floating about that the 787 may operate Sydney for BA, note there's more cargo capacity with the A380 being deployed on the 16 hour leg of the routing, so removing the 77W wouldn't affect this.