As for 18x12 prints being just fine with whatever kind of lens, sure, but what if I want to print really sharp looking 30x40 even for a reasonable viewing distance? I'll need to go beyond anything like present day 35mm lenses (especially ultrawide).
Which is why I'm sure you will be one very happy man when you get that ZD!!
Canon may be upgrading the sensors, but as everyone is pointing out, the limitation factor is now the lenses. Ergo, medium format will come back in to it's own for the market it was intended for, i.e. bigger prints.
That said, until the med format prices come down, this forum will still be awash with those complaining about canon's WA's not being up to a job they were never intended for. (the lenses that is, when they designed the 16-35L it wasn't with the 1Ds Mark V, LF replacement, in mind!)
Digital really is great, but the apparent advancements have come so da*n fast that cameras have been upgraded yearly while the
system that supports the camera is still trying to catch up.
Of course Canon is murking up the waters by trying to put is stopgaps such as the new EFS lenses, running 3 different crops simultaniously and only recently getting their digital ETTL up to scratch.
In the meantime, the technology is still immature, having a top of the line pro body with only 4fps, no anti-dust, still no decent DR in the highlights, etc while running a 1.3x alternate pro body alongside, does not to me look like a technology that has matured and has both feet on the ground.
When the digi wars are over I think that we will all give a sigh of relief and look back at the compromises we made then, and the money we spent on not yet perfect tools because of what they promised.
What camera, with what lens, for what job, we will be using as we sigh, who knows. What I do know is that it will have come of age and be from a fully mature technology, we will trust in it as a tool, one which will last for years of service without complaint.
Of course the Apocolypse may have come by then.... :p