Mr. Mango said:
Arch Exchange = merger of Lion's Arch Equities and Trading and the Xunlai Guild? =P
I don't think it is, to be honest. Well, I mean, we don't know, but I thought someone at ArenaNet mentioned the Xunlai still being around, or someone found a concept art or something. Either way, I'm sure I read a post by someone here saying that the Xunlai were still here providing storage solutions.
Ah! Found it - a GuildMag interview with Ree Soesbee:
The Xunlai and the Zaishen orders still exist in Guild Wars 2, but hold positions of significantly less prominence than they once did. We can’t tell you much about account storage, banking, and so forth, but we can say that their ties to Cantha have been mostly lost, due to the severing of all contact between the northern and southern continents because of the rise of Orr.
So it is possible
that the Arch exchange will just be buying and selling, and the Xunlai will handle storage, but there's no official word just yet.