From what I understand, the man in the middle (MITM) needs to war-drive to my network and use some tool, as yet developed, to hijack a signal from a specific un-patched wifi device (a TV for example). Is that right? Also, it looks like the hacker needs the MAC address of the compromised device. That's a lot of info not available to a casual war-driver.
Is it possible to update the router firmware to detect the key re-installation? That way, the old un-patched Squeezeboxes and baby cams could still be used, risk free.