Yes, there are tons of people with level 99 Empyrean or Mythic weapons, except there isn't, Relic weapons are the only common 99s, at best, which means that it would likely be Delve Boss Weapons, and Relics, that are primarily asked for.

Besides that, your talking about killing all of the new content? No, why? Simple, armor, accessories, everything besides weapons that they drop. Weapons are a single thing, most jobs only need 1~2 of them and nothing more, in the case of my MNK I needed Oats, do I have any need for any other H2H in the game for my MNK? No, none, they are the only ones, so I will not bother with the others, simple as that. Give me Relic H2H, and it will be the same, I will get the top H2H, nothing more. Does that mean once I have Oats all content dies? No, Skirmish and Delve as well as WKs have a ton of armor to obtain, much of which has its own uses for different things, and for that reason, keeps the content alive.

Even if they update RMEs, WoEs, and Magians, basically eliminating every weapon from Adoulin as viable choices, Adoulin gear, as in Armor/Accessories, would be more than enough to keep the content alive & active.