With the Nikon production history of updating approximately every three years, a new line of DSLR is on the horizon in the next several months. By examining the past release schedule, being the D300 in Aug, 2007, D700 in July, 2008, D90 in Aug, 2008, D300S in July, 2009 and more recently, the D7000 in Sept, 2011, the most anticipated new release is the full-frame D800, as well as D400 DX format, with a class leading rumored at 36 mega-pixels sensor. Please see one of many sites reporting below:
http://www.lensrumors.com/nikon/nikon-d800With the ending of a production cycle, it offers an opportunity to purchase the D700 FX format and D300s DX format bodies at a discounted price. The D90 is on sale near $650 compared to its launched price of near $1,100 prior to its disappearance off the market.
For photographers who are not inclined towards "must have" temperament, but rather oriented towards long term value, it would be a suitable opportunity to consider an "up-grade" (pardon for the irony) at this time. As an example, there are wedding photographers who "stocked up" on several D700 bodies because of its performance such that their work-flow would not be interrupted by the change of a new camera body. So good luck with your Christmas shopping
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Good birding and photography.