Google made lots of half baked products before and terminated them when they didn't work as expected (https://killedbygoogle.com/).
I agree with some of your points regarding scalability and add the fact that Transformer architecture (which GPT-3 was trained on) was created at Google. They also have all the data in the world to train a better model.
If you look at the history of companies that failed to adapt to new technology then you see that it is mostly when the new technology requires a significantly different organisation. For example, digital cameras are a very different beast from old analogue cameras. For Google+, that isn't Googles expertise either. Google is full of scientists and algorithm nerds, creating engaging experience or understanding social was never their strong suit.
In Google and ChatGPT's case, a chat bot that functions like an answering machine needs almost exactly the same kind of people, infrastructure and workflows as their current search team. Google could at anytime decide to make those work on a ChatGPT clone, and that would be supported by all of their search pipelines and data models and release workflows they designed for search.
Will chat make less money than search? Probably. But search isn't such a large part of Google, worst case Google will have to kill some more side projects.
I agree with some of your points regarding scalability and add the fact that Transformer architecture (which GPT-3 was trained on) was created at Google. They also have all the data in the world to train a better model.
Interesting to see what Google will come up with.