I can see why you are concerned. You are imagining something that was never announced.
The original news said something about placing targetted ads at the moment the messages are opened. There are not much more details than that.
What the news suggested to me is that Google is going to offer e-mail accounts to the users like Yahoo does. By being the e-mail provider, Google can display the messages to the users with targetted ads. But this has nothing to do with AdSense because AdSense is about targetted ads being placed in publishers content. This would be an extension of the AdWords market. Publishers of newsletters would not get anything from this.
What we, the publishers of sites with newsletters, are interested is to put Google AdSense ads in the newsletter issues that we send out.
Since we have many subscribers and even with Google offering e-mail accounts, most of our subscribers will probably not switch to Google E-mail, we could make money by placing many targetted ads on our newsletters but Google has to analyse their content.
To make this practical, there needs to be an automated way to do this so we can get the targetted ads tags to place in our newsletters before they are sent. Web services (SOAP/XML-RPC) is a possible solution. Another solution is to have an online version of our current newsletter issues so Google can analyse it before the newsletter is delivered to the subscribers by e-mail. What I am talking here does not invade the privacy of any user.