Probably not in 20 years time as the airframes will no doubt by then be considered as well past their sell-by date.
However as the 747-400 stands it is considered a very fine aircraft which is well suited to a lot of BA's routes. It's contribution in BA will continue for many years yet.
I believe it is also very possible that at some future stage stategy with regard to capacity will reverse and more 400's will be purchased. BA have never ever made a significant decision in the past that hasn't been reversed at some future time. It's a funny old world!
Regards
Exeng