I would expect the end game of this would be advertising networks injecting content directly into the page as it's rendered on the webserver. If they want tracking, at some point they'll just ask companies to hand over their logs…

Yes. Or sites just CNAMEing entirely over to their ad network, which then proxies the page content and inserts ads. Which are then, as a side effect, are very difficult to block.

And since they can easily correlate logs server side, they can track people between sites.

Oh my, what a grim vision of the future. I'm going to stop recommending ad blockers, on the theory that I don't have to be faster than the bear...

I suspect the EU will just outlaw that kind of collaboration.

I think this is the eventual goal from tracking prevention's side.