While I cannot speak for the developers, I believe they are indicating that they are going to be adding features that will work with their own branded hardware, such as dedicated cryptography chips, but will also work regardless of the platform. Embedded cryptography silicon is becoming more common, and it provides a lot of additional capabilities to developers and hardware manufacturers. If your platform has these additional capabilities, then the software will be able to take advantage of them, just like pfSense does now.
I do not think they are going to lock down the software to their own hardware or add any restrictions on the hardware most folks are currently using (hey, there's even improved RealTek support from the community). That's never been the case, and they would alienate the massive user base they currently serve.