In addition to analyzing the use of Sony sensors in Nikon DSLRs, Chipworks has also published an article that explores Canon’s full frame sensors. It’s quite technical, but the main points can be grasped without understanding the terms being thrown around:
On the process side, the 1D X is remarkable in that Canon continues to stay with the 0.5 µm process generation it has used for every APS-C and FF device analyzed. While the use of a mature fab likely gives Canon a competitive edge via lower manufacturing costs, it may also weigh heavily in its product development [...] Given the geometric constraints of 0.5 µm design rules, Canon seems content to hang around the 21 Mp resolution for recent FF sensors through the use of shared pixels [...]
So, back to the rumors of Canon allegedly readying a high resolution competitor to the Nikon D800. Will Canon finally move off that 0.5 µm generation? It is worth noting that September 2012 marked the 10 year anniversary of Canon’s announcement of the world’s first CMOS FF sensor, the EOS 1Ds [...] every Canon FF sensor analyzed since has used the same 0.5 µm design rules. It is a credit to Canon that it has remained competitive by continuing to optimize its pixels fabricated in a relatively mature process.
What they’re saying is: if Canon wants to continue fighting in the megapixel wars with Nikon and Sony, it’s going to need to shake things up a bit in its sensor department.
P.S. If you’re into comparing the technical aspects of camera sensors, check out Digital Camera Database. It has a sensor comparison tool designed for you.