1) Sony went to a great deal of trouble to design and manufacture this DAP, and thus it is in their best interests to get a good return on their investment in it.
2) Sony are making a big push into Hi-Rez music download sales, of which the NW-ZX1 and NW-F880 are a directly integral part, marketing-wise, just as Apple's iTunes and iPod have historically contributed, hand-in-hand to each others commercial success.
3) In an increasingly-global marketplace, and in increasingly competitive&challenging global economy, there is less and less reason to restrict sales of a flagship device to only one country.
4) Sony have fallen on relatively hard times, this past few years, so, given the opportunity to sell this DAP in fairly substantial numbers, globally, they'd be foolhardy to overlook that opportunity.
I could continue with more points, but I'm sure many of us are thinking along somewhat similar lines, so there's no need to labour the point.
In summary, I fully expect that the NW-ZX1 will find its way into the global marketplace through official Sony channels (albeit more slowly than through unofficial channels).