>Would someone spend $1k for one lens for their $500 D3200 >class camera? >Esp if in a year or two the lens will be useless?
I doubt Nikon will stop making DX bodies in the next four or five years. The price of an FX sensor would have to drop very significantly to bring the cost down enough to provide a decent profit margin to build entry level FX bodies that sell for less than $500.00 with a kit lens (D3100 $446.95) (D3200 $596.95). Now consider that the 18-55mm VR (DX) Kit lens is priced at $196.95 and the 24-85mm VR (FX) Kit lens is $596.95 which is significantly more than the D3100w/18-55mm VR and the same price as a D3200w/18-55mm VR for the lens alone. Considering the volume of entry level bodies sold it doesn't make financial sense for Nikon to abandon DX format any time soon.
If and it is a (very big) IF, Nikon stopped making DX bodies tomorrow, that $1000.00 DX lens will be useful for much longer than a year or two. For example: I purchased a 17-55mm f//2.8G ED IF AF-S (approx. $1200.00 at the time) to use on my DX bodies (D70s & D2X) back in 2006. I continue to use it seven years later on both the D70s and D2X that I purchased in 2005 along with the D200 (purchased in 2006) and D300 (purchased in 2007). While I also shoot FX bodies and have been since the D3 was introduced (2007), I will continue to shoot my DX bodies long into the future regardless of what happens. Good Luck and Enjoy your Nikons!