We've been eagerly awaiting detailed specification confirmation for the PowerShot G1 X Mark III, which is scheduled to be announced in mid October.
We've been told to think of the camera as an EOS M5 with a fixed lens. That should tell us it will be equipped with the 24mp APS-C DPAF sensor as well as utilizing the DIGIC 7 processor. We've been told previously that the lens will be a 24-120mm 35mm equivalent, though we don't know the speed of the lens at this time. I think you should be able to piece together what the rest of the specifications for the camera will be.
The previous iterations of the PowerShot G1 X did not have EVF's, but I think it's likely the new camera will if it's modelled after the EOS M5, though we have not yet confirmed that bit of information.
We'll update as soon as we receive more specifications.
Just a reminder that we've been told that this will be the only PowerShot G series camera announced for the remainder of the year. We'll likely see more ahead of CES in January of 2018.