Hello! I apologize if this has been answered before, but I can’t seem to find it anywhere. I know that there is a big change coming with the authenticator, so here is my question:
I don’t use the app for authentication. I have the physical keyfob that I bought a few years ago and I still use it to this day. As of January 5th, will I not be able to use it anymore? Thank you for your time. 
The physical device is unaffected. Granted, the life expectancy of those are limited, but nothing changes for those when support for the Authenticator App ends.
I have a physical Authenticator keychain. Do I need to take any action?
No. The physical authenticator is not affected by this change. However, the physical authenticator is no longer available and when the battery dies you will need to use the Battle.net Mobile App to continue using the Authenticator feature.
Thank you so much!
A deeper question might be is; if you only use a physical authenticator do you lose the in game bonus’ on the 5th of Jan once this change goes in?
It’s implied this change won’t affect the keyfob, at per the link Vrak posted.
I have a physical Authenticator keychain. Do I need to take any action?
No. The physical authenticator is not affected by this change. However, the physical authenticator is no longer available and when the battery dies you will need to use the Battle.net Mobile App to continue using the Authenticator feature.
No, I"m not sure why you would. It doesn’t depend on the Mobile Authenticator, just an Authenticator.
Some benefits, like the extra bag slots, also require that you have Phone Notifications/SMS Protect on the account. So keep that in mind.