I also do not see Google parting with something so critical to their advertising. With their own browser they control the full length of the wire between the ad-server and the user. Without it, they don't. Only way I could see this happening is if Google then released what they considered a better browser.
They've already been convicted of anti-trust behavior for precisely this reason. Now the trial is in the remedy phase where the DOJ is asking that they be forced to divest ownership of Chrome and other properties.
Google will have no choice in the matter. It's entirely up to the judge at this point.
This is not really their choice at this point. They were already found to have abused their position so it's up to a judge to decide what Google has to to next. Google doesn't need "a browser", they need a tool that allows them to exercise more control and this whole court case is about preventing that.
OpenAI is just looking for new ways to funnel data into the training of their models. And I'm afraid so many people would eat it up as long as OpenAI gives them some AI candy in return.