My take on the issue is that there are probably shooting situations where you need high ISO. Some other situations require high resolution. MFDBs seem to lack in high ISO performance but have plenty of resolution. If you are shooting sports or concerts you probably need high ISO but not necessarily high resolution, so Nikon D3/D700 make a lot of sense. Regarding architecture/landscape resolution is always nice to have but can be hard to utilize. We also need to print large to make the resolution visible, although there are some observations indicating that differences can be seen in small prints.
The ability to shoot higher ISO is always useful outside the studio. Subjects actually move. I recently shot landscape under windy conditions, even with a decent tripod (Gitzo GT3541LS) vibration may be a problem, especially if there is a play in the lens itself.
To sum up:
You need high ISO: use big pixel cameras like D3, D700 or Canon 1DIV
You need Megapixels: use D3X, Canon 5DII or Alpha 900 and crank up ISO if/when needed
I am probably just being old fashioned here but I don't quite understand it when I see lots of photographers always wanting the ability to work at super high ISO settings. The general message is that any camera which isn't capable of shooting completely clean noise free images at 3200 ISO is a pile of junk. For many years I shot every image on 100 ISO film and somehow always managed. The photographer I assisted worked with EPR rated at 50 ISO and pushed 1/3rd so effectively it was 40 ISO but again, somehow we always managed whether shooting 35mm, medium or large format.
Today I shoot digital like most others but the camera stays on 100 ISO and I am reluctant to work at anything higher than 200 ISO because ultimately the best quality comes from sticking to a low ISO setting, so if I have to use a tripod or flash that's fine. Perhaps others are taking different sorts of images, but unless you spend a large chunk of your time walking around in the dark I don't see the need for this big emphasis on high ISO settings in day to day practical use.