Next year is a Photokina year and it would be very surprising if Canon doesn't have anything to announce for the show.
By the look of things, the 5DIII/6D split of the 5D-series was somewhat rushed - without a unified vision/strategy behind it.
So, my expectation is that Canon will be working to address that.
The most likely candidate for Photokina announcement is the 5DIV, IMO.
Probably with more megapixels (~30?) and modern amenities like WiFi and dual-pixel AF.
I bought a 5Dmk2, and upgraded to 5Dmk3, but Canon would be hard pressed to sell me a 5DmkIV with ~30MP. I don't need that much, and it would have a price in computer resources needed to handle the images, and possibly at fps (or would require faster memory cards, read: money, to keep it the same).
And yes, I know about sRaw & mRaw, but DxO doesn't support those, and "ditch it for another software just so you could get a feature you don't want" shouldn't be in any salesperson's vocabulary.
I'd rather have video features, e.g. DPAF, over more pixels.
Other photographers might want higher MP, and if there's money in it, Canon should go for it. I'd just rather see it in a different cameras line, say new 1D-Studio.