Spanish Flea,
I think there were a few teething probs when the 744 kicked off - little probs like incorrect F/D wiring here & there and some fit-out problems (like no IFE on one trip I did
) - because Boeing were trying to punch them out pronto. I think it's fair to say that they'll have learnt that lesson & wouldn't want to give Toulouse any ammo.
As for compatibility... I seem to recall reading some years back (early-777 days) that Boeing's philosophy (at least re flight deck) had become one of standardise the hardware and just make changes to the software - so that a 777 jock could pretty easily (then) get to grips with a 73G and then the 7E7 (now obviously 787). If that's the case (and if anyone can confirm/deny it) then getting jiggy with the 748 surely follows.