Isn't Notion supposed to be an internal workspace for your company?
I understand the idea of cynical marketers wanting to use GPT-3 to churn out keyword nonsense to game Google Search.
But why would you want your employees reading/writing AI generated nonsense in your company's workspace?
In any case, since GPT-3 is open to everyone now, I think if you're building an AI copywriting tool (eg. Jasper and the 1,000+ others) you're going to have a rough go of it. It's now a commodity feature, not a standalone product.
As evidenced by this move from Notion, the GPT-3 API is just going to be bolted on as a feature in whatever tool you're already using.