Yes, supposedly they've found a way to make memory foam that is not as apt to make the sleeper hot. My daughter and her husband bought a tempurpedic mattress about two years ago. They don't like it because it is hot to sleep on. It probably all depends on the individual. Some folks sleep warmer than others. My wife uses very few covers while I like having a down duvet.
No, it depends on the MODEL of tempur mattress they get. I haven't delivered fur it ure since 2008-9.... and they have different models then that had different levels of breathability. If they got the bottom of the barrel that's why they had issues.
A lot of people don't understand that there is several different models under the tempurpedic brand. ... so they wrongly pass the information about the heat issue as being ALL tempurpedics, which isn't true. A good salesman would have told them about the heat issue in the 1st place. Lots of people liked it, others didnt. But as I said, even in 08 they had several models that addressed the breathability. They even have pillow top models back then with breathable foam for the top.