In Cuomo's expanded restrictions announced just this week, even open-air venues are still requiring 6 feet social distancing and proof of vaccination (one headline: "Big outdoor venues in NY can have more fans for concerts, games if they’re vaccinated". That's from an hour ago.) And those are -outside-.
Not only that, but Cuomo also announced that anyone getting vaccinated at the ballpark gets a free ticket to a game.
When the priority is clearly not "how fast can everything reopen at full capacity?" but "what can we do to make more people get vaccinated?", I don't see why they would want to de-prioritize and de-incentivize people getting the vaccine, even if the science supports it. That said, while September is a long way away, the article said that Cuomo was leaving it up to Broadway. And given that from what I hear, the vast majority of responses to surveys being undertaken by arts organizations are indicating that the bulk of audiences are extremely uncomfortable returning to theatres without social distancing and/or proof of vaccinations, in many cases until -2022-, it's inconceivable to think that the testing/vaccine option 'will be eliminated" a mere 3 or 4 months from now.
(You speculate that it will magically go away with "negotiations".... I'm just curious, if theaters can't operate with social distancing, and if I'm right that the majority of audiences are saying they won't return UNLESS people are required to show proof of vaccinations, what negotiations would you be referring to? A virus doesn't negotiate.)