It has been a while but I updated the Kali update script I have on github and added an kaliautoupgrade.sh script. They can ben found here: https://github.com/secjohn/kali-scripts
The kaliupdate.sh script has minor changes. The biggest one is I changed to dist-upgrade from just upgrade. When I wrote the script there was no difference and a dist-upgrade burned me once on BT5 back in the day so I didn't use it. The dist-upgrade seems to be needed and fine now though.
I'm on the blue team again and I now don't run everything from my laptop and having Kali on a server made me want a script for a cron job. So I edited down the script and tweaked the dist-upgrade line so conf files wouldn't stop it and made kaliautoupgrade.sh. If you have a Kali server and want to upgrade in cron, there you go. One warning, the script assumes things are there for the most part. The one time installs and checks are in the kaliupdate.sh script, you should run it once with a -a before setting up this job.
Kali Dist-Upgrade Issues Fun:
One note on the dist-upgrade, I did run into an issue with it. But is was resolvable. I got an error saying it couldn't finish and to run apt-get -f install to fix it. So I did and that failed. It said it needed to overwrite a file that was owned by another package. At the end it gives the deb file that has an error. If you run into that what you need to do is:
dpkg -i --force-overwrite /the/path/defilegivingtheerror.deb
apt-get -f install
That will let the file be overwritten. After the apt-get -f install finished you need to run the apt-get dist-upgrade again. I had it fail again and had to do the same steps above a second time. Life has been good since then.