Here it is late in 2013 and there is no 56-megapixel Nikon DSLR, no professional high-res Nikon camera body, and no sign of any Canon DSLR to compete with the Nikon D800E.
Is the high-end DSLR done for? That seems unlikely, but wow, the Nikon D800E is now 16 months along and still no D4x. And Canon is really long in the tooth even if one counts the incremental 5D Mark III.
Or are Nikon and Canon biding their time with something really exciting? Perhaps a true-color sensor or something fundamentally better. Or a paradigm shift to omit the mirror box and to provide ultra high grade autofocus accuracy via direct sensor readout. All such things would feed into a delay.