As much as many call glamour the end game for FFXIV, it's rarely at the top of the list of things players look for when choosing a new game to play. Very few would leave this game just because another game out without restrictions on their glamour system unless the other game's gameplay was as good if not better in the player's eyes.
As for spontaneous group activities, those are player created. The game at most provides a location. Nothing that the Gold Saucer offers is spontaneous - it's all either on a schedule or handled via roulette. If anything happens there, it's because the right players were present at the right time to make it happen. It could just as easily happen in other locations where lots of players hang out.
If you want to bring up a recently released MMO as a possible threat, try naming it so others can make their own judgment. Considering I'm not hearing of any that are getting any sustained publicity, it makes me think that no such game exists or it isn't a MMO.
What MMORPG hasn't been used as a waiting room by a large portion of its end game players? I saw the same thing happen in WoW and RIFT. I don't understand why people try to make it sound unique to this game. The only real difference is that FFXIV allows you to enter a duty instance from just about anywhere. With WoW and RIFT, it would be chill in the big cities until your party is online then head to the dungeon/raid entrance to go in. Done? Return to the big city to chill again.
FFXIV has its flaws but so do other games in the MMORPG genre. People will jump from one to the other, and get excited because there's all this new to them content to do but once they get caught up they start to see the shortcomings of what they're now playing.
No MMORPG is going to last forever. At best, they'll hang on with a tiny core of loyal players paying enough to keep the servers online. SE is aware of player concerns but they're still going to make the game they want to make.
Rather than worry about what is to come in the gaming future, worry about whether you are enjoying what is available to you now. Not everyone is looking for the same things in a game.