Both Sony and Canon will announce Full Frame cameras with around 50 Megapixel during the first quarter of 2015. Those cameras will likely be displayed at the CP+ show which starts in mid February.
The Sony 46 Megapixel FF camera will almost certainly be a new E-mount A7 (or A9?). It will feature an advanced autofocusing system based on the current A6000 hybrid af camera.
Canon is likely to announce a new DSLR with such a 50MP sensor. But there is a small chance Canon could use that sensor also on a new Full Frame mirrorless system camera.
I am 100% sure those kind of sensors are coming early 2015. We have an exciting time ahead of us!