If you look at Nikons release dates for their DSLR line, you'll notice that they release a new or updated version of a body about every 18 months.
See Table below, this Blogger template pushes it down
OK, so it's not that clear that it's 18 months. In the D1x/h -> D2x/h it was several years jump. Same with D100 -> D200.
But things have changed since back then. Is the D200s or D300 due out this Spring?
|D1X||2001/02/05||18 months since D1|
|D1H||2001/02/05||18 months since D1|
|D2H||2003/07/22||29 months since D1H|
|D2X||2004/09/16||43 months since D1H|
|D2Hs||2005/02/16||18 months since D2H|
|D70s||2005/04/20||16 months since D70|
|D200||2005/11/01||44 months since D100|
|D2Xs||2006/06/01||20 months since D2x|
|D80||2006/08/09||16 months since D70s|
|D40||2006/11/16||19 months since D50|
|D200s / D300||2007/05/01||projected 18 months|
|D3h||Overdue||projected over 23 months|
|D3x||2007/12/01||projected 18 months|