Unfortunately, that is not true. At least not as simple as you make it sound. BambuLab printers are not made via one mainboard, as, for example, a Prusa. You have several different PCBs all over the printer. For example for the X1C you have:
- Machine Controller board
- Application Processor board
- Screen
- Extruder board
- Extruder interface board
- Heatbed Sensor interface board
- Heatbed Piezo interface board
And I am sure I have forgotten one or two.
This is for example also the reason why the X1’s screen does not work with the P1. The AP board is completely different. Same with the hotend, it is completely different to the X1’s. The only part that is the same between X1 and P1 is, as far as I know, the two heatbed interface boards.
So, even if you can keep the mounting spots for the AP mainboard the same, you would still have to replace a ton of wiring, several different PCBs all over the printer, change some other parts, etc. It would be a major change!
The only time, this would work, if they are just reworking, lets say the machine control PCB. But they would have to keep all external connections the same, could not add any new sensor, not change a sensor to use a different protocol, etc. Only then, you could just replace one of the PCBs with a newer version.
But I highly doubt this will be done for any new machine. It would limit them hard.