I'm not sure about 'entry level' full frame. The first reason is a comment I read a Sony rep make in an interview, which appeared to suggest the A900/A850 were expensive to make and did not have high enough margins (although this could be Sony trying to justify SLT). The second reason is that I think a lot of this speculation is simply a reaction to the D600 rumours emanating from the NR website. Nikon certainly have more room to manoeuvre than Canon, especially with the existence of the 24MP Sony FF chip (and rumours of an updated version on the way). What would an 'entry level' full frame Canon look like? Realistically, there's only two choices of sensor -the 5D MkIII's 22MP and the 1D X's 18MP; not much of a product differentiation. I can't see them using the 18MP sensor, as I think this would devalue the 1D X psychologically by implying that it uses Canon's 'budget' FF sensor. So how else to differentiate from the 5D MkIII: less weather sealing, <100% viewfinder, slower frame rate, smaller image buffer? They're all a given (I would think), but Sony's experience with the A900/A850 would suggest that this isn't enough -a major product feature would have to be omitted. I'm guessing that would have to be the fancy AF system, which would leave the camera as little more than the 5D MkII with a slightly improved sensor. Unless Canon can knock them out at a very low price point, which might disrupt their APS-C line-up (refer also to my first point about the A900/A850 margins).
With regard to the 7D MkII / 70D - I don't think that there is room for both models and an 'entry level' full frame camera in the market; I feel that the 7D MkII and this '6D' (or whatever) would be a bit too close in price. I could be wrong -there may still be a market for a 'screaming beast' 7D MkII (which I basically see as a 5D MkIII with an APS-C sensor and probably a faster frame rate), at a similar price point to a basic full frame 6D.
Now the 'big if' -the high megapixel body... I know there's a lot of interest from 1Ds MkIII owners in a 1-series body that would truly be an upgrade. After all, it is these people that choose to pay (extra) for a slower, but higher resolution camera than the 1D series. Having said this, I think that it would be a mistake for Canon to choose to make their only high resolution body a 1-series camera. Nikon did this with the D3X and proved that whilst this approach gets you the kudos, it doesn't generate the sales.
Finally a quick word about mirrorless: I'm now convinced this will be a big part of Canon's Photokina plans. All the technology that Canon needs to make the perfect mirrorless camera is now in place and prototyped on other models (large sensor in a small body - G1X, on-chip phase detect AF -650D [/Rebel Kiss XXX, or whatever] , STM lenses). I call it the perfect mirrorless camera because all the models introduced so far have one flaw or other (though they are steadily improving). Let's hope that Canon can use their two years of observing the mistakes of others and produce the definitive mirrorless body accompanied by a strong lens line-up at launch (and a good roadmap).