I assume you meant:

> What I expect is that Chrome will be designed to leave Google ads alone, so that Google doesn’t get affected.

I agree with your analysis, but I'm surprised with your conclusion. I think if there's a monopoly that decides which ads are decent, it will cause the overall level of the ads to be higher, which is better for users - at no extra cost to them.

My rationale (and I'm very interested in the opposite opinion, if you're willing to explain it) is this. A monopoly has too much to lose from frustrated or unhappy users. If too many people become too angry, they'll eventually cause a major damage to the ad industry through political action, greater popularity of ad blockers, people avoiding websites with too many ads, or people becoming desensitized to ads (leading to a dramatic reduction in ad value). A small company won't really care if its ads damage the industry -- it's not there for a long run, it just needs to push its products and long-term effects are something it worries about. A (near-)monopoly that controls 20-30% or more of the market worth $100B's a year is going to be really, really careful about even the slightest damage to the industry.

As to your other point, CPM/CPC costs are not dictated by Google. It's a marketplace with supply provided by publishers, and demand created by advertisers. Google influences the prices by choosing the auction rules and by saying which ads are acceptable, but any large shift in prices can only happen from a change in supply/demand. So I'm not sure why you think a monopoly would cause a rise in CPC. If anything, a monopoly would make the marketplace more efficient, taking out intermediaries who take a big cut, and lead to lower prices (as for example happened with Amazon in online retail).