A couple of weeks ago, Phil Askey on DPReview suggested that there might be as many as 25 new DSLRs released this year.
And I wonder whether as underwater photographers we should demand that housing manufacturer's make housings for all of these, or whether we should accept that there will not be a housing for ever model, but those housings will be cheaper and have better ergonomics (as a result of housing manufacturers having to catter for less models).
How do we demand this? I don't get it. Do we somehow coerce the government to legislate that all manufacturers must make housings for all models? Absent this, it would seem a silly argument.
Our demand is that of a consumer. Manufacturers pick and choose based on demand. If the demand is there, someone will fill it. I would guess that in hindsight, there were many housing models that were a financial failure. So, if anything, housing manufacturers make too many models.
While I love my Subal housings, I would be the first to admit that my Subal D2X does not have the attention to detail of a Subal F5 housing. It was also a damn sight more expensive. Of course it works and the ergonomics are perfectly acceptable, but I miss those good ol' days!
By demanding housings for ever model of camera that comes out we cause the housing manufacturers to spend less time on each housing and with the consequently shorter production runs we drive the price up. Maybe if we did not demand a housing for every DSLR we would have cheaper, better housings.
Right, off diving.
Alex
First, the good ol' days were never that good. Selective amnesia keeps us talking about them. Housings are no different than any other consumer product. The shorter the product life cycle, the more expensive they will be. The shorter the life cycle, the more critical design to production time becomes, hence the product will lack some of the details of longer cycle equivalents. The shorter the life cycle, the less process engineering on the existing product, e.g. the first Subal F5 housing may not be near as wonderful as the last one.
We, the people with the cameras, have less control over housing demand than you may think. As camera models come and go, the consumer and housing manufacturer must follow. The first time buyer of a DSLR can't and don't want to buy a D100 or a 20D. They can no longer be bought new. So the housing manufacturer has to produce new models.
p.s. Personally I think that they should just make a housing for the D3X and stop! 
Listen to yourself, Alex.

You are stopping the clock at a model that doesn't even exist yet. That's so easy. Sounds great now, but once the D3X has been around for a few years, we will wishing they would just stop at the D4X.
I think the market will take care of itself. There may be 25 new models, but I bet there will likely be housings for less than 10, maybe even much fewer. As an example, Ikelite's website used to be filled with compact digital housings. Now, not so much. They have staked out a couple of brands and that's it. Would any manufacturer in their right mind design a housing for a Pentax DSLR? I see a dearth of housings for Olympus, Sony and Sigma, and so it will remain.