The D300 replacement, if a year away will really hurt Nikon in losing its strong position in the class. A year is getting to be a very long time in digital systems. By that time of course priorities will likely change. Now they are putting a lot of effort into video. In a year when the DSLR sized sensors will be finally put into real video cams, the interest and demand for DSLRs with high end video will stop, the form factor and lack of video industry standards compliance has meant these so far have been primarily marketing gimmicks rather than useful tools for videographers.
The lower value of some currencies have caused prices to escalate, so even though the D300s came out at a much higher price than the D300 was selling for at the time, it was really, in real dollar buying power, a slightly better buy than the original D300 which was priced in dollars worth more. The D7000 is selling for less than the D90 when it was introduced if based on buying power of the currency.
Jason makes the point that D300s did not require any major improvement to cause a lot of people to upgrade. The difference between it and the original D300 is rather minor, compared to the radical shift in positioning of the D90 successor. As most trends in electronics point to smaller dimensions and weight, it might be Nikon's long term view is that the future of a large heavy DX camera is not likely to be long, and only being introduced to keep a 5-10% of its current customer base happy because of physical layout habits. Most development and sales are going to smaller boxes that perform at levels that only large and heavy were expected to in the past. As the new wave of users come to buy Nikon size and weight will be more important and marketing can see that already in sales figures. Other brands are making inroads primarily over the size and weight issue. Cameras in the D3 class are important, not in sales/income (if it was so important supplies would be increased to meet demand)but rather as a flagship that casts a positive light on the whole brand due to being used by a good number of known and influential pros. They have no problem getting D3s's. That suggests that it really is not that profitable as a product as it is as a promotion tool. The D3100, D5000, D90 and D7000 sales really are important since they greatly outsell the rest of the DSLR models. The D300s sale are already probably frozen, it in not even in the Amazon top 100 in sales. A new model to replace the essentially dead D300s sales if delayed much longer will concede the semi-pro body market to Canon and the D7000. To the new buyers of semi-pro style cameras the D7000 IS a semi pro camera every bit as much as the D300s was. Users on the D300 forum are falling all over themselves trying to come up with reasons their camera is better than the D7000 and all it comes down to is 1 switch and 1-2 buttons, all three of which simply use a different and just as or more efficient method of input. That is not a very convincing list for new buyers of that class of camera.
Those who want to wait surely should, what is the argument about? In the mean time the IQ and noise leader in available DX models is the D3100. Stan St Petersburg Russia