No, at no point in a games life should the entire world become obsolete. I can't stand flying mounts and how the destroy worlds. If quick travel is what you are in search of, then ask for player variations (i.e ports, sow, and all that). And I am still confused on why an upgradable ground mount system couldn't help you get through grey zones? You could still move just as fast, BUT you are moving fast in the actual world, not above it. I hate to come off the wrong way, but flying mounts are about the worst idea for this game (imo of course).What about 2 years down the line and having to re run grey zones to get somewhere? Would you agree flying mounts remove that headache?
Join the war against flying mounts!