Thermoplastic polyurethane (TPU) tubes shouldn’t have issues with increases in pressure due to heat as the pressure increase is much smaller than people think…on the order of 1 psi increase for each 10°F increase in temperature. TPU does start to soften at 80-85°C (185°F). That temperature would be difficult to achieve on a rim brake wheel due to the thermal mass of the rim, tire, and tube as well as due to the radiant cooling provided by the surface area of the same. If you drug the brakes down a very long hill, you might be able to get to that temperature but it would be tough.
TPU tubes aren’t all that new. I recall them being a thing in the early 90s. I had one for a tube in a belly boat in that era. They never really caught on for a couple of reasons. Since they are not completely puncture proof, patching them was a problem which seems to have been at least partially solved. Sizing was also a problem as the polyurethane tubes of old did not stretch. The size of the tube had to be matched to the size of the tire very carefully. And then, as now, they were expensive.