If you are asking about the blue glowing one, that's the ascalon catacombs skin during the night. The dull one that precedes it is its day version. The golden one after it is the one from caudecus manor.
If some fractal maps and a few events to southshore is all the real content that's gonna be added in the next few months, then I can see why they needed to add so much grind to keep people playing and interested. Too bad it was gear grind...
I have never once based my buying decsion on how many copies a game sold
Many people will though, considering this is an MMO. Player population has a major impact on post-launch support, longterm enjoyability and the general longevity of the game.
As for the number sold, I'm sure it will go up by quite a lot between now and launch seeing as how many people probably held off buying before a release date was given, which was pretty recent. And that's not considering all the more casual/more skeptical people just waiting for post launch to buy.