Dead Money is due to be released exclusively for Xbox 360 on December 21, priced at 800 Microsoft Points ($10). Of course, Fallout 3's DLC was initially described as "exclusive" to PC and Xbox 360 but later hit PlayStation 3 too. All we know for now is that publisher Bethesda clams up tighter than a very tight tight thing when questioned.
And so it begins. I haven't bought FNV yet due to my backlog of other games. Looks like I'll be waiting for the FNVGOTY edition to bundle all DLC in one fairly priced purchase.