This is picture of my ZEN mount for S&S. Is it possible to change it (I am thinking yes...but I don't know how look any other mount for some other housings)?
P.S. I didn't get still yet any answer from S&S company about my question about UW housing for D4!!!
This is educated guess work - I've not done any of this.
I think to change it from Sea & Sea to a Nauticam then you just undo the allen key bolts around the side and bolt on a Nauticam adaptor instead. There is probably a o-ring in there too.
To change to other mounts it probably requires a new backplate on the port. Which would be much cheaper than buying a new port. I am sure Ryan or someone from Reef Photo (who are the guys behind the Zen dome series) can confirm this is possible and give an indication on price.
The other option is to sell your existing port (quality domes tend to hold their value well) and buy a new one. I know that your dome is in perfect condition (I even have photos) - better than new. No tape anywhere! :-)
To get back to the main question - I think for the time being the best option is to wait. It is easy to identify the 3-5 housing companies that are doing D4 housings - that you would consider. And I am sure we'll start seeing housing designs very soon.
I don't see the D4 being hugely popular underwater (I see far more people using the D800, for many well documented reasons). It will be adopted by those who recognise and need its specific abilities. As a result - I don't think there will be big waiting lists on D4 housings, so there is time to see the options and then make a choice.
I have not seen any D4 (or D800) housing renderings yet. But I suspect that we'll see some housing designs on the front page of Wetpixel coming out very soon.
p.s. Good to read the clarification on Sea & Sea's position.