As someone that works in a data domain, I'd say it's unlikely the ads are served on a single conversation basis in the near future, if they even are today. Any modern data org like advertising is optimizing metrics of conversion (either optimizing for increasing profits via CPI increase or revenue by increasing advertising TAM presumably).

Introducing context beyond immediate conversation history will improve conversion rates & allow targeted advertising towards wider topics or higher CPI topics (like financial products), hence it's inevitable.