Timing could also depend on what Nikon is going to be doing with the D400.
I don't believe a word from anyone who says that Canon is waiting for Nikon to see what they do with the D400. Do these people who spout off statements like that think that even Canon, having their own chip fabs, can conjure up a sensor, firmware, amplifiers, or even a new battery and get it all into a usable, rugged, reasonably bug-free camera body (keeping in mind tolerances are on the order of microns for pro camera bodies) in a matter of weeks? No, the prototyping for a product of that scale takes months, and getting anything even remotely ready for delivery can take a year or two. It's not even a matter of throwing more money and engineers at the problem (at a certain point adding more engineers makes the project unmanageable - a lot of the design for each component is the result of linear thinking).
I don't think they're going to base sensor design on what Nikon does with the D400. If they do that, they are ceding the market to Nikon for the next two years. They might play with announcement and delivery timing (I'd suspect Canon to announce after Nikon and deliver before Nikon since Nikon preannounces way too far in advance) but that's about all the impact Nikon would have on the 7D mk II - if there will be a mk II (I hope there will be).
I see people comment like this all the time: "Canon is holding back the nD waiting to see what Nikon does" or "Nikon is holding the Dn back to see what Canon does first." No, the reality is R&D takes time, and they're each sufficiently successful and have such a strong revenue pipeline that they do. not. have. to. rush.
and instead bake the product until it is actually done.
They can crank out rebel after rebel after rebel because for key components they're just drawing from their existing parts bin and forking software projects, with minor tweaks so development and QA efforts are minimal, and offer a huge return for minimal investment. For the XD line (and the XXD) it's a different matter, since those models usually get the sensors, software, and other bleeding-edge components first. That's also why the xD and xxD models cost so much initially - the first unit to roll off the assembly line cost tens to hundreds of millions of dollars to product - the second about half as much, and so on until R&D is fully amortized, enabling Canon (and Nikon) to lower the price, as the sales morph from recovering losses to earning profits. See: amortization.
It's one thing to add a gimmicky articulated screen to a low-end camera body using screens from your parts bin and make a new plastic mold, and tweak sensor designs you borrowed from pro and semi-pro cameras and get the product out in a month or three, and quite another to develop a whole new hardware and software architecture (as well as a fab process, metal casting molds and precision machining tooling with a tolerance of a few microns for a mass-produced product) from the ground up.
If there is ANY truth to Canon basing the product on Nikon's announcement, it would likely be choosing between a selection of workable prototypes that are similar enough that the tooling for parts is already in place for each, or could accommodate minor variances with minimal effort. They're certainly not going to get a whole new chip fab process designed, tested and scaled up for production that quickly.