ACMS,
Qantas ordered their 787s before BA, hence it's probably reasonable to assume that Qantas would get priority in the 777-as-compo pecking order (especially as QF is the biggest Dreamliner customer to date). If they've been offered to BA, I suggest it's safe to assume that Jim's already been chatting to Geoff.
And the conspiracy theorist in me says that as Boeing has become increasingly aware of problems on the 787 line, they have kept a few places on the 777 line up their corporate sleeve as a contingency. So we should not be too surprised to see some rabbits being pulled from hats.