The Internet of Things is going to be unmanageable if we keep building it out of general purpose computers. If we must have smart devices, we should use special purpose computers with fixed, first order functionality. Not only would updates not be necessary, they wouldn't be possible.
One of the main reasons we use general purpose computers is because their generality allows us to use the same computer for pretty much any application, so we can benefit from an economy of scale by mass producing lots of them knowing we'll find a use for them. I think it might be possible to get similar benefits from special purpose computers used to build a set of fundamental controls - there are only a relatively small number of ways we control the devices around us (ex. toggle switches, dials, etc) and since each of those fundamental control types would be common across a number of different devices, a smaller economy of scale could still be achieved with special purpose computers that drive such controls but with the benefit of lower maintenance than can be achieved with general purpose computers.
You'd never be able to build a toaster that sings to you that way, but why would you want to?