I think the problem will be (is not a problem yet) that relatively experienced FOs will stop signing up when they realize that even with all the shiny jets coming online there will not be enough expansion to "guarantee" an upgrade.... Emirates will turn in to a classic legacy carrier where an upgrade is 10+ years away for a new joiner. Someone provided a rough calculation on airframes and upgrades in the ME forum and it looks like this is already something new joiners should consider before signing up.....