Except a lot of the automation devices don't use Ethernet, but other bus protocols, and maybe central low-voltage power. Which you might be able to send over Cat6, but I wouldn't bet on it, especially if you want to get it professionally installed.
I'd be very surprised if the standard IoT ecosystem that ultimately wins out doesn't use standard 110 V lines already in the walls for power and WiFi for data. Realistically I am not seeing it being worth it for the average person to spend many thousands of dollars to rewire their entire homes when the alternative is to simply get much cheaper devices that use the wireless network you already have and plug into the wiring and outlets you already have.
