A separate press release says it will be available for S$1299 from late January. This works out to about US$$899 before sales tax. [Correction: The actual press release says S$1199. I was misled by several articles reporting the price as S$1299. This translates roughly into US$829 before tax].

It's official now. See, eg, https://www.sony.com.sg/walkman/products/nw-zx707 Has USB DAC support, according to a Japanese youtube video linked from thewalkmanblog site.