Same situtation of me... I use D70 since the product release.... I still want to plan to upgrade... either D300 or D3.... if you have no budget D300 is only one choice.. beside that... if you plan to have D300, but I don't think you buy any DX lens anymore.... may be 4 years after... you will have FX format.... and all DX lens will useless...
... Try to think to upgarde the lens to 24-70 f2.8 first.... and wait for body price drop... body always have NEW... but good lens can last for 5~6 years... For me... if D300 price around $11-12K or D3 around $30~31K... I think I must go ahead... that why I plan to upgrade the lens first!!! ... of course if you already have good lens on hands... D300 la....