because of IBIS.. no.
you can deactivate it on those cameras and afaik it doesn´t make a difference.
the A6300 had no IBIS.
also other cameras don´t overheat.
but it could be that the sensor can´t be cooled as good because of the assembly.
less surface contact for heat dissipation.
Yes, that's what I'm saying. It doesn't matter if you can turn IBIS on or off. It's not the functioning of the IBIS that's generating the heat. It's not even a matter of more heat generation with IBIS, it's a matter of dissipating the amount of heat that any sensor generates.
If the sensor is capable of IBIS, that means the sensor and all of the hardware that dissipates heat from it now must be part of that assembly that moves as part of the IBIS. If you have a sensor that's firmly mounted in the camera, you can attach all the heat dissipation hardware to it that you want. Your only limitation is space within the camera and the weight of the camera itself.
As far as the argument that they don't want to have IBIS so that they can sell more lenses, I think that's some serious tinfoil hat thinking. Canon is not the only company to ever make IS lenses. Trying to cling to an old technology when there is a better alternative out there just for the sake of clinging to that technology is foolish, and not a winning strategy. That's why they're finally embracing mirrorless, and why they will probably similarly embrace IBIS, albeit a little late to the game, when they feel that the technology meets their standards. And as has been said, lens IS is not immediately irrelevant and useless just because you have IBIS. They could have even better stabilization performance if they had both.