In the last 3 or 4 days, the D800 took the 1st place on amazon.com again, while 5DIII was second. I just checked again now, and the D800 is still no.1, the expensive D4 @ no.3 and 5DIII @ no.4
Considering that Canon has more users than Nikon, and that very few actually switch brands (usually), and that the Nikon cameras were available on Amazon for more days (Although there was a pause in sales for some days), these numbers are not that positive for Canon. Amazon is just one seller, but I think they are big enough to get an idea of what is going on.
If this trend proves to be true, and if it is long term sustained after the cameras are available and tested, might be possible that after the initial big demand diminish compared to their supply, Canon might decrease their price.
Don't get me wrong, I love Canon, and the 5DIII is great and I am going to get it, but we can't consider this camera overall better than the D800. They are nearly on the same level with differences which might prove better for some or others. I shoot sports, and the extra 50% odds to get a better shot with the 6fps is a preference for me, but certainly not better overall, and not worth the extra $500.
Although there are users which are willing to pay more than $3500 for the 5DIII due to personal value, overall this camera can't reach this value and the market (at least Amazon) is showing it. Again, this is good for us for a possible price decrease earlier than thought. Or is just wishful thinking ?