
The Raspberry Pi 400 was definitely a curveball. Looking like a Raspberry Pi keyboard, inside the case was a SoC similar to the Raspberry Pi 4. And according to a device tree overlay spotted by Hackaday It seems that Raspberry Pi is working on the Raspberry Pi 500, a version based on the current flagship Raspberry Pi 5.
Over on the Raspberry Pi GitHub repository for the arm64 OS we can see arch/arm64/boot/dts/broadcom/bcm2712-rpi-500.dts, which is the first device tree overlay for the Raspberry Pi 500. And it looks like it will use the same Broadcom BCM 2712 SoC as the Raspberry Pi 5.