From SONY ALPHA RUMORS:
"I got a peak behind a curtain at the CeBit today:
The A7 M3 will be likely announced in April/May with a great feature set.
The newly developed 22MP sensor features world fastest FF autofocus system. The Exomer RS sensor will also feature vastly increased readout speeds. It was designed with both still image and video image quality in mind.
This results in expected features of full sensor readout for all video modes (including 4k). Optionally pixel binning and line skipping can be activated for stunning slow motion video recording at native resolutions."