Are you going to manage the updates of the core components (vs gems) like Postgres / Redis etc ... ?
The goal is certainly to help you upgrade Postgres and Redis. One of the tricky bits of this is that often times your code will be affected by this, so I don't want to accidentally break your apps.
Once there's a major version update, I'm going to be working on a script to help you do the migration as seamlessly as possible. The process is usually pretty simple for Postgres where you only have to run a couple commands to stop the old database, migrate it to the new version, and start the new version. You can see the process here: https://gist.github.com/delameko/bd3aa2a54a15c50c723f0eef8f583a44
Redis is similar, although, it's probably easier to upgrade than Postgres which is great.
Hatch won't take over full control of your servers like Heroku does, so you're free to upgrade things at any time or make changes as you like. At the end of the day, I want you to have full freedom to run what you want and have Hatch just make your life a bit easier so you're not dealing with the hassle of server management constantly.