I'm an anti-advertising zealot (#BanAdvertising!) but I share `brookst`'s view on this not being much of a concern. Brand advertising does exist (as opposed to 'performance' or 'direct' ads), but there's a few reasons why trying to sell ads baked into SotA language models would be a hard sell:
1. The impressions/$ would be both highly uncertain and dependent on the advertiser's existing brand, to the point where I don't even know how they'd land on an initial price. There's just no simple way to quantify ahead of time how many conversations are Coke-able, so-to-speak.
2. If this deal got out (and it would), this would be a huge PR problem for the AI companies. Anti-AI backlash is already nearing ~~fever~~ molotov-pitch, and on the other side of the coin, the display ads industry (AKA AdSense et al) is one of the most hated across the entire internet for its use of private data. Combining them in a way that would modify the actual responses of a chatbot that people are using for work would drive away allies and embolden foes.
3. Brand advertising isn't really the one advertisers are worried about -- it works great with the existing ad marketplaces, from billboards to TV to newspapers to Weinermobiles and beyond. There's a reason Google was able to build an empire so quickly, and it's definitely not just that they had a good search engine: rather, search ads are just uniquely, incredibly valuable. Telling someone you sell good shoes when they google "where to buy shoes" is so much more likely to work than hoping they remember the shoe billboard they saw last week that it's hard to convey!
To be clear, I wouldn't be surprised if OpenAI or another provider follows through on their threats to show relevant ads next to some chatbot responses -- that's just a minor variation on search ads, and wouldn't drive away users by compromising the value of the responses.