With the Privacy Sandbox Google already prepared for their sell side ad business to be sold. With the ad auctioning logic and data flow being handled directly in Chrome PS they wouldn't need GAM anymore and would probably easily accept this part to be split. And it could even reinforce their vertical integration. On the other hand with no direct access to the browser and no 3rd party cookies anymore, they would probably be less relevant for media buyers on the open web, which could open a good chunk of the market for other ad platforms.