That's more "device" pairing than "parts" pairing. The thermostat to HVAC communication is a standard. Sure, if someone started forcing that, that'd be bad. But that's more akin to Apple's "iOS only works with MacBooks" type shit with Airdrop and such than it is to their "you can't replace the camera in your phone unless it's from us". They're both problems, but the one you're describing is both not happening and a different issue. I'm not saying it won't happen but it's a different topic.