I reckon part of this is to have out engineering and maintenance before too many 787s arrive. The 767s were retired early to get rid of LAMEs off the tarmac as well as a whole back of house support system. If they get rid of those 744s early the 787s won’t yet be at a place to need heavy and thus the engineering support for the 744 will also be made redundant and gotten rid of. Therefore when the 787s finally need maintenance there will no internal capability and it will have to be off shored.
Then we really will test whether these new aeoplanes need less maintenance than the previous generation.