For those for whom price is never an issue, buying the newest and the best may be the way to go, but not all of of us are in that situation. Buying a car just before - or even just after - newer models have been released can be a practical approach to solving automotive needs, and the principle is also applicable to camera equipment.
The fact that the D100 is - or soon will be - out of production shouldn't itself put the camera and housing out of consideration for everyone. Used bodies at more reasonable prices should be available for some time to come, and prices for new and used housings may come down as well. If an older camera-and-housing combination meets the photographer's needs as well as more costly newly released cameras and housings, then the older model gear can sometimes be an optimal solution in a very expensive field.
My first underwater housing was the Subal Miniflex for the F801s, a Nikon body that had long been out of production when I bought the housing for it. The housing was much less expensive than a comparable housing for a newer camera, and I was able to purchase two bodies in excellent condition for less than the cost of a new, in production body at that time.
A top-of-the-line new model camera such as the F90 or F100 would unquestionably outperform my F801s on many counts, but only at much higher cost. I've taken photos with the F801s that I'm very happy with, and I'm sure I will take more.
I still use the F801s when my digital housing is in for servicing, as is the case right now. In fact I used it just yesterday, on some dives ( molas and mantas ) here in Bali with visiting wetpixel-ler Alex Mustard.
Frogfish