Maybe as you say, because they really don't have anything now that can match Nikon when it comes to sensors (or, more hopefully, they have something in the wings, but want Nikon to think they are still stuck in the past).
If you know or remember Paul Pope from DPReview, this well-informed guy has this to say:
"Not the best they could do by any means but rather the best they were permitted to do by the bean counters concerned with wafer yield in their sensor manufacturing...
But don't be too concerned the best Canon CAN do is still to come ..."
"I believe Canon's latest sensor technology is going to be showcased later this year. The video camera gives us a hint of what's to come I'm told."
"I don't believe its a 5 series camera .... more like a 1DXs type of thing.
I think it shoots video at a bit more then 1080p as well ...."
So, we can expect the high megapixel sensor to appear in a 1D body. And if the engineers manage to convince the bean counters they have the yield under control, we may very well see the latest sensor technology from Canon in it.