Matter, HomeKit compatibility, and buying a home security system

Hearing about CHIP/now-called-Matter, I’m curious if anyone has dug into what this means for existing HomeKit compatible devices. If I were to buy a home security system that’s HomeKit compatible, will it by nature become Matter-compatible? I assume part of Apple’s view on this is that Matter will bring in all existing HomeKit devices, but I also don’t want to spend money on a system that would not be compatible with Matter. Do any of you know about this? My goal would be to have something I can control in the Home app or other HomeKit app that controls those devices.