Gmail is getting suggestions for what to unsubscribe to in the latest version of the app, which users should be getting updates to soon enough if they haven't started receiving the update to Gmail already. Users will be able to activate this feature from the settings menu via a new toggle under inbox tips settings, with the option labeled as unsubscribe tips. Once the box is checked Gmail will start to keep an eye out for emails that come in from specific addresses that may not get checked often, and once it's able to recognize these email lists it can make suggestions to unsubscribe to them so you don't continue to get emails from a service you almost never interact with.
This is the only new feature that seems to have been added to Gmail as of this moment but it does appear that Google has some other stuff in the works for a future app update, so although they may not be available right now they'll be coming down the line. One of these features will be the ability to set incoming notifications to a priority that only focuses on emails which are labeled as high priority. So if you get emails often throughout the day, you'll get notifications only for those which are extremely important.
Another upcoming feature looks to be email bundling, where Google will be grouping emails together that are part of the same type of category. At first it looks like Google is going to start implementing this with promotional emails but may expand upon it later on in the future. With bundled emails users should be able to keep things a little bit more organized as multiple emails will be lumped into one listing. Since these features were found in the code of the Gmail APK there's no telling how long it will be before they're rolled into the app.