The Nikon D2xs was shipped earlier this month, but many found that there was no raw converter support for the new camera. In response, Nikon is offering a 30-day trial version of Capture NX on its Web sites. Capture NX supports the D2xs directly. Capture 4.x may go through additional service fixes in the future. The official quote [now revised] I got from them is "we will release service updates as we determine necessary for Capture 4, however have no plans at this time to add additional camera model support to Capture 4." That seems cryptic to me, especially since I asked directly about D2xs being supported by Capture 4.
Meanwhile, that still leaves those that use other converters up in the air. Here's the thing: the only differences between a D2x and a D2xs NEF image are the Camera ID tag and some additional Maker's tags in the EXIF. The additional Maker's tags can be ignored, I think: all you have to do is change the Camera ID tag from "Nikon D2xs" to "Nikon D2x." You do this by changing the hexadecimal value at offset 161 in the file from hex 73 ("s") to hex 00 (end of field marker) using a file editor. On a PC, you can use Hexedit; on a Mac you can use 0xED. Or, if you're a non-geek type, you can use the automated tool, D2XsHack.