Google Assistant is likely to get custom hotwords soon as evidence found in the APK of the most recent version of the Google App seems to suggest that Google is already trying to prepare the Google app for this kind of support. There are currently no hotwords mentioned specifically, but the code inside of the APK does mention that it will be possible to teach Google Assistant to recognize a hotword that allows it to activate similar to now when you say Ok Google or Hey Google, then users would be able to follow up the hotword with a particular command that they want Google to complete.
Since this is just code in the APK at the moment there's no detail on how long it might actually be before Google implements the ability to set up a custom hotword and train Google Assistant to recognize it, but this is something which users have expressed wanting, so for those that are wanting this feature hopefully it'll be available sooner rather than later. In addition to setting up custom hotwords in the future, it also looks like Google is finally getting Google Assistant ready to allow for a secondary language. Under the settings for the app, in the Google Assistant menu, there will be a new sub-menu listed as "language" which will house the primary and secondary language options.
Beyond the Google Assistant changes the Google app is also going to be supporting offline downloads and syncing of podcasts at some point in the future. Once this capability is live, it looks like downloaded and synced podcasts will be able to be stored for a certain period of time, and users will have the option to have them automatically removed after 30 days, or 24 hours after the user has finished listening to the podcast, which isn't too unlike the setup for movies that are rented from Google Play. It's not clear if this auto removal is an optional setting or if it will be on at all times. Other more minor changes coming to the Google app include switching the Assistant Voice menu to being called Voice Selection, online routines, order delivery status, and support for Duo on smart displays, such as the recently announced JBL Link View or Lenovo Smart Display.