Installing Raspberri PI version

New to kali (though not Linux).

Yesterday I downloaded file kali-linux-2020.4-rpi4-nexmon.img.xz did the verification, wrote it to my SD card, and booted it up on a Raspberry PI 4.

So far so good. But I also read the recent announcement that the default shell would be ZSH for this latest version. It was bash.

Suspicious, I pulled up a terminal window and typed:
uname -a
Linux kali 4.19.118-Re4son-v7l+ #1 SMP Wed May 6 16:33:16 AEST 2020 armv7l GNU/Linux

So, there's no reason for me not to use the latest version. How do I upgrade?
=== Al