I will upgrade when I make a foolish impulse buy and the retailer doessn't fail to deliver by my required date.
I learnt a long time ago to always make time of delivery an essential condition of orders to supply goods which are in short supply (time of essence). I have found it as useful to cancel foolish impulses as it was to put pressure on deliveries. Thank goodness that my chosen supplier could not supply a D3 within the month from my order in December.
My D200 is good; it is better than I need; I do not need a D3 or D300. Now that both cameras are available I must remain disciplined and not upgrade until Nikon produce an equivalent to the Canon EOS 5D at a sensible price and weight.
For the time being I am safe because all spare cash accept an emergancy fund is tied up in 3,6, and 12 month investmants, but by March temptation will be rearing its head.