Comment by mnau
How big percentage of customers even logged to their home router. It will be way below 10% (I would wager in lower single digit percents).
So
* manufactures open source it
* "someone" is going to maintain it, for free
* all these people are going to find non-malware infested fork
* upload custom ROM to their devices.
I just don't see it.
Automatic updates/killswitch are the only way forward.