The detailed specs for the Sony a290, which replaces the a230, have leaked along with photos of the camera. So why should we Nikon users care? Because the a230 uses the "same" sensor as the Nikon D3000. So guess what, the a290 will probably be the "same" sensor that will be in the rumored D4000. So I'm gonna bet that the D3000 will be replaced by the D4000.
The new sensor is a 14mp CCD with the same ISO range as the current camera (100-3200). But if Nikon puts this sensor in the D4000 the biggest news is that it WILL NOT have video! The a230 (old Sony model) and the a290 (the new Sony model) do not have HD video! So that to me makes it very likely that the new D4000 won't either!
So if you want HD video from a Nikon then your cheapest choice will probably still be the D5000. The D4000 will be a "cheap" entry level Nikon with better ISO noise control and more megapixels than the D3000. It'll be priced at about $500USD. The D3000 price will probably fall to around $400!
I hope I'm wrong but I don't see where else Nikon could get a low-budget sensor for a new "entry-level" camera. Just wanted to throw this out there so you guys have time to "adjust" to "yet another" Nikon DSLR with no 1080 video. Maybe...perhaps.