Word from Thailand is that the D5000 replacement has been in production for a bit now, and that containers have started to be loaded. That means an announcement must be near on that camera, though I have no useful details to report. I think the only real question most of us have is whether it contains the D3100 or D7000 sensor. My guess would be the former, otherwise doing a separate sensor for the D3100 doesn't make a lot of economic sense to me. My best guess? Next week or the first week of March would be the likely announcement time frame, and it won't have a lot of fanfare, as it's likely to be just the D5100 and perhaps a lens. That's the type of thing Nikon does by press release, not formal get together. Nikon's next big announcements (I believe there will be two, plus lenses) won't be until late March or more likely early April. April, by the way, is looking like another cluttered announcement month. At least two other camera makers have targeted that month for new announcements, too.
Meanwhile, one interesting rumor that's circulating is that Nikon thinks they need a less expensive entry DSLR. I suspect some of the mirrorless models hitting as low as US$399 in closeout may be driving that. But with the NEX-3, E-PL1, and GF-2 running at US$599 and the NX100 at US$499, there's a lot of pressure at the low DSLR end right now. Can you give up a bit of image quality and focus performance for much smaller size and weight? Sure. Plenty of people are doing it. As the rumor goes, it has Nikon bringing back the D3000 as a lower-cost entry camera. I'm not sure I believe that, as that seems a little bit of a stop-gap type of measure, and I've not known Nikon to go that route. I'm also not sure how that would produce a lower cost camera, either, unless Nikon has a bunch of sensors and imaging ASICs laying around from that generation that are already paid for.