Olympus have just announced the EM-1 MkIII : https://www.dpreview.com/reviews/olympus-om-d-e-m1-mark-iii-initial-review
The body looks very close to the MkII, but looks like they have done just enough with buttons to make using MkII housing difficult. The rear screen/EVF button has moved slightly and the menu button is right next to it now plus the info button is now a joystick.
Some interesting new features but not too much for the UW shooter. It now has 7 stop stabilisation, improved weather sealing (IPX-1) and new face and eye AF algorithm. There is also a live ND mode and handheld high res modes. The weather sealing sounds impressive - rated for 10 minutes in the equivalent of 1mm/minute rainfall.