In terms of actual data, they have lost anywhere from 80% to 90% of player activity since launch per Xfire. Website traffic to sites like Guildwars2.com and GuildWars2Guru have dropped 80% since launch. Per Raptr, GW2 is on par with SWTOR in terms of hours played (and SWTOR is supposed to be a "failure"). The traffic of /r/guildwars2 has also dropped 70% to 80% since launch. Again, all these various sources show a 70% to 90% drop in players.
Now this is not unique to GW2, many MMOs come out have a peak during launch and fizzle. GW2 also followed the same route, it is just like every other MMO out there. It is not special it was not "more successful". Today it is on par with SWTOR. But the future isn't so bright. NCSoft is putting all their money behind WildStar, so don't expect any big expansions from GW2. At least not while WildStar is around and popular. That is the reason Mike told players not to expect an expansion, the game doesn't have NCSoft's attention.
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I would love to see a source on that January stat you posted. That is impossible, since most data said a 70% drop from Sept '12 to Jan '13. If your source is Colin, please read what he wrote again. There is nothing factual about your statement.