If there is no content out there, the whole flying vs no flying debate becomes a rather moot point, because the open world might as well not exist at all to a lv 100 player.
So for now: we need them to fix the content issue first. When people are actually leaving their Garrison and DO stuff out there beyond: "take afk FP to Apex loc -> kill mobs for 10 minutes -> hearth back" that's when they will get fed up with the constant waste of time of ground mounts and start harassing Blizzard to put flight back in.