Most outfits operating the B747-400 will be reputable and seniority will be observed. Therefore any upgrades can take time. Air India have and had, a few late 30's early 40's IIRC.
However there are one or two outfits who have got their hands on 744's now, where seniority does not exist. AAI for example, where there are probably individuals (with little conscience, let alone experience) have "jumped the que". Try them as there maybe some surprises.