If you simply offer a useful service (and I believe I do with the recently launched http://anynewbooks.com) I don't think you are going to be terribly impacted. People will always open emails that they find valuable whether they are newsletters or not.
If all you offer is low quality bacn though, you're going to hate this new Gmail feature.
What I'm saying is that it's not the death of newsletters. This new feature is really useful and its negative impact on permission based marketing can be reduced by ensuring that the content you send out is really appealing to your users. Which is a win-win situation, because more appealing content usually leads to more conversions.
A high open rate may mean that your newsletter ends up in the high priority inbox for a decent percentage of your user-base, despite being a newsletter (unless Google automatically excludes newsletters).