Their model is shipping ESP devices flashed with open source firmwares. They still go on their own firewalled wifi network, but this is about as future-proof as I can imagine: the software is open source, the updates can be run locally, the parts they're made of are actually pretty simple PCBs you could get a fab run of your own done if you wanted to.
In terms of "future" proofing, everything I've installed I've been putting in accessible junction boxes well labelled - electricity isn't going to change, so as long as it fits in a box, I'll always have the option to replace the hardware (if you have light switches with a neutral wire then you're basically set).
I wouldn't say "simple" per se but that's really more on the "you need a box running some type of home automation stuff". I suspect simple enough for the consumer would be something which came with it's own wifi AP and pre-configured mesh routers so the IoT network would start out intrinsically separated.