Well, I definitely agree that a key theme to this excellent short story is the way that technology has replaced, or perhaps it is more accurate to say outlived, humans. However, I find it hard to see how a theme of humans replacing technology can be extracted from this story.
Let us remember that we are presented with a level of unprecedented technological sophistication in this story. From the very first sentence, it is clear that mankind has reached new heights of scientific knowledge in this world which they have applied to make their lives easier. The house is able to manage itself completely, ironically without the need for humans at all:
Out of warrens in the wall, tiny robot mice darted. The rooms were acrawl with the small cleaning animals, all rubber and metal. They thudded against chairs, whirling their mustached runners, kneading the rug nap, sucking gently at hidden dust. Then, like mysterious invaders, they popped into their burrows. Their pink electric eyes faded. The house was clean.
And yet perhaps this is precisely why Bradbury creates such a world. The story, because it contains no human characters, operates as an ironic reflection on the strengths and weaknesses of human nature. It also functions as a warning about the dangers of technology. After all, it is the same technology that has created the self-governing house above that is responsible for the creation of nuclear weapons that has resulted in the extinction of mankind. Bradbury forces us to confront hard questions about the use of our cleverness if it is not moderated or seen in context with our intense vulnerability in the natural world.