Yes because it would prompt more people to buy it. I won't because by the time it comes out I'll have all the DLC and will be looking forward the imminent release of FO4.
Don't count on it. I have a feeling that they won't release by the end of 2012 (2 years after the game released) and before then, DLCs and Skyrim will likely be their focus. So it wouldn't really make sense that they'd announce the new Fallout right around when they might release a special edition.
However, all expect is all of the DLCs, and maybe the preorder packs. But it doesn't concern me because I own the game and all current DLCs, and will continue to buy future DLCs.