Did you get this figured out? We're about to try the same thing. I have all the changes queued up in a BETA channel build, but beta channel users see the new app with the previous name and imagery.
I'm fairly sure the title of the app when you create it in the developer dashboard is permanent. You would have to create a new app with your new title and copy the code into that. As far as I know that's the only way at this juncture 😕