Just like Nikon is pursuing multiple offerings, so is Canon. These have been in development for the past 3 years, and the tech is being released for the current generation of bodies just as the new projects kick off for the next gen in 2014/2015.
Canon perhaps has it more difficult as it is producing both the sensor & supporting processors, whereas for at least a significant amount, Nikon uses Sony sensors. Nikon only has the imaging business, and their focus not unreasonably results in aggressive products - which is good for everyone. And Sony still want to play heavily in the digital camera market for all sorts of reasons which is also good for competition.
My guess is there will be 2 further Canon dSLRs this year. One as CR guy states in March and a "larger MP" one in the Autumn if the D800 goes well.
I think the March release will aim squarely at a 24MP camera from Nikon / Sony. Just not sure about the FF/APS-C piece. I think this will be a different camera to try and disrupt Nikon.
How large a MP the autumn release will be does depend on the success of Nikon, but clearly a newer version of the 7D sensor upsized to FF with better processing by a Digic 5+ will probably stand them well.
I don't think Canon is panicking in any way, they're just playing cat n mouse with Nikon & Sony. Some of the participants in this forum, clearly are more worried than Canon