Right now there are some darn fine mirrorless cameras out there that beat the 7D for almost everything except focus speed/accuracy and decent glass to hang off of the camera.... It could happen.... I'd bet not soon, but as long as we are wildly speculating based on a tiny shred of evidence, why not make it a really wild guess?
Why not make a really wild guess? Well your guess is wilder than my expressed wish that they abandon 1.6x and go 1.47x, or whatever the image circle will tolerate. And yet I got told "oh that won't happen, that can't happen, you're wrong". I wasn't even predicting it would happen, only suggesting that it should
happen. Because the sensor needs to be as big as possible, and still work with the aps-c image circle. I mentioned 1.47x, because I feel Nikon's image circle isn't all that tight on the corners of the sensor. If it were, there would already be a noticable tad of corner vignetting, and there isn't.
I'm talking about a sensor that is probably less than 0.70mm bigger, along the diagonal, than Nikon-Sony's. So I say it is
possible. For that matter, why do we need to keep the 3:2 aspect? Why not go 7:5 aspect? 7:5 is by far the best compromise of all the sensor aspects...4:3 is too square, doesn't use enough of the image circle's width at wide angle. Or best of all, why not a multi-aspect sensor, that truly makes use of the image circle?
I'm not sure the future includes sensor-based autofocus that is equal or superior to separate AF-sensor-phase based. If the future was heading in that direction, we would have seen some element of it on the 1Dx or D4. Whatever Sony does with it, I can't say. I know they're using a transparent mirror for their top aps-c camera, even now, are they not? Does the future include transparent mirrors? You're suggesting those will get leapfrogged in favor of on-imaging-sensor-based phase AF, correct? In the far future, sure I think it's possible. In 5 or 6 years maybe?
Lacking focus speed accuracy and "decent glass to hang off the camera", are kind of like lacking electricity...But are you referring to a Sony body, or a M4/3 body? (Surely you're not referring to a mirrorless Nikon body??) Because I don't see any M4/3 body matching the 7D currently. What beats the 7D now, sensor wise, are the D7000 and D5200, and perhaps a Sony body, even possibly the Nex 7?