There's never been any overheating issue. The issue was idiots leaving their devices in direct sunlight and using cases while charging.
In other words, the reports have been about misuse of the devices.
Though there have been a few rare cases of batteries leading to fires, that affliction applies to every single battery driven device made in the last oh decade at about the same rate.
What you'll learn quickly with Apple products is that, even if they have the same kind of occasional problem as every other brand, if it's on Apple, it will be a huge issue worthy of front page news for some reason. Apple has quite a few zealous fans and haters alike.
Anyway, there's nothing to worry about regarding overheating assuming you're following operating procedures laid out in the manual (remove cases while charging, do not leave in direct sunlight, do not use in excessive heat as noted by operating temperature ranges listed on apple's website).
