Sony A7s. Confirmed 12mp Full Frame sensor and 4k video means 1:1 pixel use (no artifact/binning issues, more accurate color, etc.). Low light should be damn impressive too. Full announcement coming this Sunday (4/6) at NAB.
And unlike the GH4, a metabones adapter already exists that allows aperture control and IS for EF glass on E mount bodies.
I hope Canon is paying attention, beyond discounting the 1D-C.