I find the heat issue very disturbing. There is a need to have this small sized camera for video work on a gimbal. Few years back I used 7DII to shoot TEDx conference. It was one time job in a life. But I did it. I'll still wait for a full frame camera with interchangeable lens that can shoot 4K/60, unlimited recording time and a decent codec. The R mount and drop in filter adapters could solve even the ND issue on DSLRs. With little money we could add that feature found in cinema cameras. But, I guess, Cannon won't offer this for a low price. 1DXIII has no issues regarding overheating. R6, instead, for less money, with the same sensor, has this problem. Finally everything is about marketing, about money. I'm happy that Canon somehow answered. It's a shame.
EDIT: overheating is real: