You do not own the software that makes the device what it is. Yes, you own the physical console but you don't own a single piece of OS code, they do, and if they want to change their OS code they can and barring popping fuses they haven't damaged your console and certainly not criminally.
Hmm, that's an interesting point for the courts to thrash out. Does a company have a right to change the software on
my machine? If MS wants to download some OS update that'll brick my PC if I run software they don't like, is that really allowed? If I buy a console, it is bought as being suitable for a purpose. The software is part of the package and is required to make the machine work - we don't just buy a bundle of components. When I buy it, it works. Now if I change the firmware to my own and the product still works, the console company loses all liability, but I can't see that extending to all circumstances. So if the CFW bricks the PS3, that's my fault, but if Sony do something to brick it, that'd be theirs. However if it's part of their service, they are entitled to change software.
You know, the long and the short of it, I think the way things are actually highlights exactly how it works. If ahcks and creating CFW is illegal, GeoHotz would be arrested. Everyone knows who he is and they can grab him for his iPhone activities. But they haven't. Likewise console companies do remove features from hacked consoles, but they are services to which one adheres to a contract to use said services. MS isn't destroying XB360s, only limiting their online functionality. Thus if someone wants to buy an XB360 and install a CFW for their own ends to work as a media server, they are allowed to do that (as in, the law and MS's lawyers let them) but they can't use the online components which requires another XB360.
Hence, it seems to me to play out that owning, installing and developing CFW aren't illegal activities. You are free to do what you want with your purchase. Console companies don't have a right to control how you use your product, but they do have a say in how you use their services and it's these that they can lock users out from. Managing future CFW is a matter of anti-hack measures and updating FW with services etc. to ensure users online aren't able to run CFW, just as it is now. There won't be cases of CFW creators getting taken to court for enabling piracy because they aren't responsible for how pirates use CFW; no more than a browser creator is responsible for someone using it to hack a website. If the console companies want to get draconian, they can enforce online connections for every use, but I doubt that'd help them sell consoles!