I don't understand this claim. They are still calling hot devices laptops today. Do you mean that at some point in the future they will stop, and then they will never again call these devices laptops?
That's true, but I have a hard time believing it has anything to do with the fact that their laptops can get really hot. It's clearly marketing to differentiate themselves from their competitors.
Apple stopped using the word 'laptop' when they were still struggling with trying to put a G5 in a portable computer that didn't require jet engine fans.