You have to differentiate between two things:
CanBoot:
Is a bootloader by @Arksine that can be installed on certain boards. It will allow to flash new Klipper firmwares easily without having to attach the device via USB or SD-Card. See here for a how-to on the SKR 1.3 / 1.4 boards: CanBoot: Flash BTT SKR 1.3 / 1.4 / 1.4 Turbo
To profit from new CanBoot updates you need to install CanBoot on your devices, for example following above linked how-to.
Can Implementation in the Klipper Firmware
The Klipper firmware natively supports to use Can Bus as an addition / replacement to USB / Serial connections. This means that you connect additional MCU boards via Can Bus instead of USB. If in addition CanBoot is installed on the MCU the full benefit can be achieved.
The recently announced Can improvements relate to the firmware implementation, making it more robust.
The respective PR has already been merged. All you need to do is to update the Klipper firmware on the MCU. See Frequently Asked Questions - Klipper documentation