I'm not from BA, so could be completely wrong about this - although I have got quite a few friends at BA who I heard this from....
Although lots of newcomers have been taken onto the 777, there are also now quite a few internal BA pilots who have just got their bids back and have been given the 777 - although they may not get a course till next May.
So all the guys/gals who are joining now and for the next year will effectively be at the bottom of the seniority, therefore getting the worst trips etc, won't they then continue to be at the bottom as all the longer-serving BA lot move onto the 777 with their mugh higher seniority number?? It could be then that those going straight on the 777 will pretty much have a not-so-good roster for a pretty long time??