If you use a different DevID than your last pkg you published, you will wipe the registry section for your app on every roku that updates and runs the app. This will start the app in a "freshly installed" state. So if you store data in the registry it is imperative to always use the same DevID and password. The pkg can be used with the pkg password to extract the DevID on any roku model. In this way you can "port" your developer stuff over to the new roku and begin development from there.
You won't be assigned a new AppID when you use a different DevID. So you are safe there. You will upset customers if you store things in the registry to let them register, then later they have to do this again because you published with a different DevID. This will cause your bounce rate to inflate as people will become confused why does it have them set it up again. Since you aren't keeping anything here, you should be good to go either way.
Thanks for the info. I think I'm doing it right, I have rekeyed several Rokus now and never got a warning uploading new packages. But yeah I'm not storing any data at all, the channel can't do anything unless you open the app on the phone.