Oh, it certainly is, and it's naive to think it's not.
While they haven't released sales figures for the gem shop, I think it's safe to say that you could credit just about everyone in the game for purchasing one $20 bundle of gems. This is accounting for people that have bought no gems, and people that have bought obscene amounts of gems.
On top of the 3 million boxed copies sold (and that's a figure from January, so it could even be closer to 3.5 - 4 million now), that's about 1/2 a game purchased again by those same people.
So maybe it's not surpassed the boxed sales numbers yet, but the pace at which it's making money for Arena Net is much higher than it ever was for Guild Wars 1. If they've made this much money in less than a year, then it's safe to assume that they'll surpass the GW1 mark in a relatively short amount of time.
And that's not a knock on GW1, because I love GW1. GW2 just has things going for it that GW1 never did, such as a lot of pre-release hype a really active gem store.