I would totally LOVE a native mac os x client.
But there are a few things you do need to know before jumping to this question.
I am not sure what GW2 uses for engine, but for a native client, this engine also needs to be native, if this engine needs porting too, well time/money consuming.
There are alot of good working cider ports out there, tweaking and debugging can take you quite far. The fact that they started a mac port means they are at least seeing a serious possibility for mac gamers. now we just have to convince them we need stability and performance as well