So Google would need to build a discriminator that detects machine-generated content. It will be interesting to see these discriminators fight the generators of other big companies.
I'll be taking a front-seat row watching that show, if it happens. Perhaps in the future, we'll have to deal with discriminators that approximate some originality-index. Will be fun fighting with those algorithms, to interact with the internet as a normal user (to some extent we already do - proving that you're human is becoming more and more tedious.)
In practice I think it's more Google now has another policy reason to banhammer prolific and irritating blogspammers than an arms race Google has a chance in.
Google isn't yet effective at detecting blogspam generated by naive scripts that simply swap words in the source material for other words in a thesaurus. I don't think they're going to start picking up continuity errors, factual errors or "weirdness" in GPT-3 - which often satisfies human readers - any time soon.
Google engineers can't even filter out GH or SO scraped sites like gitmemory, nor offer a way to let users block these sites. I'm not sure we should expect them to handle more advanced techniques like detecting word swaps any time soon.