There's enough room to tinker with the dimensions that adding a temperature probe seems feasible. Like the stem of the Pros is actually shorter, which was clever because it means people know you have the fancy new ones. This couldn't add more than a few cubic millimeters.

Breath tracking is pure software, offloaded to the phone, opt-in to auto activate when in exercise mode.

I think we'll see both in the next few iterations, the fitness push is huge and the temperature monitoring would be timely. We'll see.