GPT-3 is great at sounding coherent, but much worse at actually reliably solving problems. I absolutely see GPT-3 like things aiding with sales decks, but... it won't replace the sales person.
There's also a large component of enterprise sales having a "trust" component where you know your counterparts. You're not spending approval-worthy amounts of money after only having talked to a chat bot.
Also, if your competitors are using GPT-3 to solve customer problems, having an actual, intelligent human can be a formidable differentiator in terms of customer experience.
If there's a sales person whose job is to tailor sales decks to use cases, you might replace them.
If a big sale takes a team of people to execute, maybe AI cuts a few of them off. Maybe the client is still talking to a real sales person when they need to, but that sales person is able to multiplex to more clients because the time they need to put into each is reduced.
I think people often miss this aspect of "X technology will make this job obsolete"; it isn't "that occupation no longer exists" as much as "far fewer of that occupation are now necessary to do the work", and that change can have meaningful economic impacts. Farriers, blacksmiths and calligraphers still exist, but their work is no longer core to the function of anyone's economy.
Salespeople says BS to sign you up, only vaguely coherent, backed by some basic database facts about the product/price, so GPT can handle that. Think about Donald Trump: Huge fan base of paying customers, barely distinguishable from a chatbot.