You'd most probably wouldn't be able to tell for sure. Ads will be subtle and flow as background music to the onversation. Talking to the AI while on your daily commute will make you thirsty for some sort of hot beverage while ChatGPT tells you all about sirens in Greek mythology.
But why the hell would I want to talk to the AI while on my daily commute? Do people do that?
do people really think like this? or is this satire? i mean what kind of subtle ads do you see in youtube and why do you assume it will be the case in llms?
if you believe that you haven't been paying attention. Have you actually used AI much? Current ones couldn't subtle their way out of a paper bag. I have no real reason to believe anything in future would be different.
In general, any textual embedding in the ad or system prompt would result in an abjectly terrible user experience. I must assume it will just be banner ads etc