I can say after seeing the D800 in Yokohama (at CP+) yesterday, the rumors of the 45MP 5DX had better be true. Nikon has a clear winner on their hands from what I can tell after playing with the camera. As a mainly studio photographer, the D800 really appealed to me. The images I shot with it were nothing short of amazing! I was blown away by the detail I saw on the camera's LCD, so I can imagine how great they would look once I got them into Aperture or Lightroom. I really hoping Canon answers back with this 45MP beast. 2012 is going to be an interesting year for photographers for sure. I was considering upgrading to a Leica S2, but if Canon and Nikon can produce similar or better image quality in a camera priced at a fourth the cost, Leica just lost their entire S2 market.
On another note, I also had the opportunity to play with the Canon 1DX, but since it's off topic here, I will post my thoughts about it on another forum.
I don't like the idea of a 45MP beast to be honest. The images are from D800 do look superb, but I can see a lot of potential buyers are worry about the file size, the storage, the processing time etc. If Canon put a 45mp on the market, these problems can become more serious. As a result, those buyers will go toward to D800 straight away, because the D800 suddenly becomes a more balanced camera for them. And I don't think the high ISO level of a 45MP camera can match the D800.
If Canon are into high MP beast, I hope they can release a similar MP as the D800, let the IQ decides which one is better.
BTW, Lecica has a totally different market.