I'd expect the 16 series will improve on battery life and thermals in general, but honestly anyone holding out hope for something radically different is almost certain to be disappointed for a very long time.

Smartphone batteries are more than sufficient for the vast majority people's uses. The 15 Pro has a battery which is apparently nearly the worst out of the 14/15 series line up...and I'm still hovering around 40-50% after 5 hours of use, depending on exactly what I was doing that day. That's around 8-10 hours of battery life total.

If I'm spending enough time on my phone for this to be a problem, even after 3 years of degradation, I probably have larger issues with my life than phone battery.

Meanwhile, even a battery that triples this battery life is going to still just get charged daily because it's too short to charge on a regular, easily remembered schedule.

There's a reason why Apple has, and will continue to, favor focusing their battery improvements on fueling new features first before allowing them to trickle down to actual battery life. We're at a point where battery life isn't realistically a concern for the average user, and is a more niche feature that most of the stuff they might want to spend that extra battery life on.

It's going to take a small revolution in battery technology for us to see major leaps in how long these devices last.