An issue brewing for some time now with the recently released lenses will finally have to be adressed by the housing manufacturers.
It seems the trend toward very large diameter lenses is clear. I think this will only get worse now that both Nikon and Canon are in the full-frame business.
The new AF-S NIKKOR 14-24mm f/2.8G ED is 3.9 in in diameter, making this the fattest UW apropriate lens that I am aware of. With its ultrawide (weitwinkel) angle, fast speed and rectilenear projection, I'm sure it will be on every UW photographers wish list regardless of DX or FX format. But given the wide angle and fixed shade I'm sure this will be a difficult one to house and get sharp corners from (No diopters).
Even the new AF-S NIKKOR 24-70mmf/2.8G ED is 3.3 in. Both of these lenses will require a zoom gear to make them useful necessitating even fatter port diameters.
The last fat lens in common use was the AF-S VR Micro-NIKKOR 105mm f/2.8G IF-ED at 3.3 in diameter. This is the lens that sent all the Subal users to the lathe. Despite a special port, Ikelite still has no manual focus solution for this lens.
Before that was the AF-S DX Zoom-NIKKOR 12-24mm f/4G IF-ED which at 3.2 in just barely fit with a zoom gear in my Ikelite port (you actually have to mount the lens after the camera is in the housing making boat battery changes even more hazardous.).
The industry largely ignored the 3.4 in diameter Sigma 12-24mm F4.5-5.6 EX DG. But I think fat lenses are here to stay.
I think its time to re-think the standard port design that is so limiting to these wider lenses now that 3.9 in is the new 3 in. I don't think it will do to continue with kluged up custom port solutions. Perhaps a wider port opening and a new set of wider port extensions should also be on the list for D300 and D3 housing designs.