Let me throw a few numbers at you and you'll see that the next few months in Nikon DSLR-dom is going to be a bit different.
The D3000, D3100, D5000, D7000, D90, and D300s are all made in the Thailand plant. That plant has a maximum capacity of somewhere over 3m units a year. Let's be generous and say 3.6m. That's 300k units a month.
So, how much demand do you think there is for D3100 and D7000 DSLRs at the moment? 300k units a month? I'm betting that the initial demand is going to be higher than that. The D90 was Nikon's best selling DSLR, and the D7000 is, on paper, clearly better. Meanwhile, the D3100 is better than the D5000 (except for the positionable LCD of the D5000) and is currently selling for about the same price. Guess which one will sell more?
Full D3100 production started last month, and full D7000 production started this month. How much do you want to bet that these two models consume virtually all of the plant's production capacity (300k units/mo) in October, November, and December? The initial D7000 units are going to sell out immediately is my guess, which means the plant will be scrambling to catch up on that model. Meanwhile, the D3100 is selling briskly enough to put another big demand on the plant.
So what happens to the D3000 and D5000? Well, I think they go away when the current inventory built up of those models is exhausted, which could be before the end of the year. That's because there's not a lot of ability to build more with the plant trying to catch up on the other two models. Ditto the D90 inventory, especially if Nikon brings its price down any more (currently US$899 for the body).
And so the Nikon "out of stock" problem is about to get worse. Come early November, we'll certainly be adding the D7000 to the growing Nikon inventory management problems, as the initial month's production won't come close to matching demand.
Meanwhile, all of you are asking for Nikon to come out with their mirrorless system, a D300s replacement, a D700 replacement, and more. The manufacturing gurus at Nikon are already working overtime trying to meet demand. Don't expect anything to change for the better soon.