I took this opportunity to do a FULL BACKUP of the phone (there is no 1 Android app that backs up everything), Factory Reset, update to 5.1.1, and then restore everything. This is not a quick process and data loss is of course possible. I only did this because I was having pretty significant problems with the phone.
To backup my Samsung Galaxy S5 phone, I used:
Google (Accounts -> Google -> all checkboxes checked for syncing)
Export Contacts to .vcf
SMS Backup and Restore
Move all my photos, videos, ringtones, downloads, documents etc. to my PC using USB3 cable
Took notes of which apps and widgets were on each page of my Launcher/Home screen
AT&T is probably going to make us wait another 4-8 months. Remember, Samsung downloads the Android files from Google and works on them. Then AT&T downloads the files from Samsung and loads them up with crapware and all kinds of unnecessary changes. And sometimes, after all this work, the carrier decides "screw it, we'll just sell them the new model".
I've found it useful to take a screen shot of each screen. Then you can send them to yourself in an email or save them on Google Drive. When you restore, you'll see exactly what each screen looked like.