Big tech are bigger than ever, they've simply learned to double dip with pay to play and ads. AI is also going to do both, but I think they have stickiness to extract a lot more per month. Like once a generation grows up with AI crutch, they will shell out $$$ to not write their own emails, for the simple fact that they never really learned to write all their own shit in the first place.
I don't think you're wrong re: their hope to hook people and get us all used to using LLMs for everything, but I suspect they'll just start selling ads like everyone else.