There will be no migration to this because its not useful at all (as a HeaterMeter). It lacks features of both the Pi and the ATmega needed to be in parody with the current system. It doesn't have the wifi, the ram, CPU power, nor the storage capabilities of a Raspberry Pi. It doesn't have enough ADC inputs to replace the ATmega. It does have some cool features on its own which makes it better than an STM Blue Pill for other projects, but I don't think there's a place for it in the HeaterMeter ecosystem. I have a hard time considering it though when you can get an ESP32 with similar capabilities which also includes wifi/bluetooth for around the same price point.
The Pi compute modules are cool too, but they rely on somewhat high precision SMD soldering to mate to anything I'd design which kinda makes them a non-starter. I'd never design something using those connectors and expect an amateur solderer to put it together, which means it would just have to be a manufactured product which people would have to source from me. Being open source as well, then anyone would be able to make a giant batch of them and sell them for cheaper so the risk is too high for me to make them, which removes any motivation for me to spend time making it. They are cheaper than a Pi4 too, but some of that cost would be eaten up by the cost of manufacturing the other half so the price isn't too much of an advantage.