Normally when your title has a gimmick, you hit that gimmick for all it's worth. Mario has jumping and mushrooms. Sonic has speed and rings. But when your gimmick is little more than wings attatched to an otherwise bland role playing game, there's not much you can do aside from watching your subscription base wither and die against games that are in reality light years better than itself.
In other words, wings a good MMO doth not make.
Such is the fate of Aion, though in reality it suffered from a number of issues over its subscription based lifetime. Mid-to-Late game content was non existent for the longest time and it banked far too much of its draw on the ZOMG!Wings gimmick that added next to nothing in terms of gameplay. Stronger titles continued to nibble away at its marketshare with the final nail in the coffin undoubtably pounded in by Old Republic. On a side note, that's the good thing about strong titles making their way to market place-- They weed out the crap and lets be honest, Aion was little more than another pretty version of Rift. Or Rift a pretty version of Aion, whichever you prefer because these mediocre games are all but interchanable.
But as is the trend these days, all is not lost for you the gamer. There is life after failure to profit and it appears as if Aion's wings will carry it into the afterlife of free to play, cash shops and all that crap. I'm not sure it deserves it, but it will undoubtably get more eyeballs than it had before even if they can't guarantee revenue from one day to the next.