Are you even suggesting that at some point it is reasonable to introduce a cooling process that makes the coffee cooler, or to have coffee stand after it is poured before handing it to the customer?
Does any place that serves hot coffee do this? Have you ever drank a cup of coffee?
Last things first: not only have I consumed coffee, I grind my own beans at home. (I
never drink or order hot liquids when I'm planning on being mobile.)
Second: if 165 degrees is deemed to be unsafe for human consumption, there are many potential solutions, including, but not limited to, introducing a cooling process.
Another possible solution is for the legislature to act (as I said) to resolve the issue, perhaps by making it illegal to dispense coffee over a certain temperature into any form of "to-go" container or drive-through window. Or removing liability for this kind of injury.
Regardless, the fact remains that evidence showed McD's coffee was hotter than the industry standard- McD's coffee temps were found to be between 180-190 degrees (i just checked)- and that is key. In PI cases involving product liability, industry standards are the first thing you look at (after relevant laws, of course). If your company's practices are outside of the industry standard, you will be asked to justify your variance. If your variance makes your product more dangerous to the public without some reasonable* justification, you're simply opening yourself up for liability. If, OTOH, you can show justification- public health, whatever- your liability may be limited or even negated.
* Reasonableness is decided by the Trier of Fact (a jury or Judge, depending) Here, McD's simply wanted to have hotter coffee, possibly to satisfy a subset of customers who wanted ultrahot coffee. They did so at their own risk, as shown by decades of settled lawsuits and one entirely avoidable landmark loss. The Trier of Fact found no justification for McD's variance from the industry standards.