Since most of the rumors coincide with “new” sensor technology, and significantly lower noise; My guess is that Canon has further evolved the Dual /( Multi) CMOS technology to acquire more light, while maintaining resolution???
Perhaps distributing pixels over multiple sensors, with a method of acquiring “even” light to each sensor element. ( The only “current” manner of lowering APS-C noise is to reduce resolution/pixel-count.
Canon has a history of “field testing” new technology in lower priced cameras, hence the 70D.
I do expect that the 7D MK II will be a big improvement over the mk I.
I do not expect more than one sensor in the camera, why would they use multiple sensors?
You cannot acquire more light by splitting a pixel in pieces, they gather photons according to the area, so you receive approximately the same number of photons overall. The 70D does not acquire more light, but uses the dual pixel for phase detect autofocus. Otherwise, its the same as other Canon sensors.
The split pixel technology potentially allows some other tricks like improving DR, and probably some that I'm not aware of.
Maybe dual sensors could be used, but not for what you think. I could see a use to have multiple sensors, 1 for imaging, one for AF, one for the hybrid viewfinder (or maybe a dual pixel sensor that can perform AF and feed the hybrid viewfinder.
I would be willing to bet that the new models will just do away with the phase detect sensors that we know and have loved for all of these years. A better full time contrast detect with higher speed AF with focus points anywhere across the sensor field. Higher end models would be fully programmable on AF patterns. Lower end would be fixed patterns.
We have already heard rumors of the 7D replacement having a larger "bump" on top. How about a specialized prism that can split the image into multiple paths to multiple sensors.
It just seems to be the next logical progression from the dual pixel technology.