pmensky said: "Well, that would certainly reflect what I said earlier about a big star not wanting to share the spotlight with another big star, but I figured they’d at least hire an actress known for her work on Broadway. I think Gayle Rankin is a tremendous talent, but I think if she is the choice, most people’s initial reactions will be, “Who?”"
I am in no way affiliated with the revival, but have it on quite good authority that Rankin is indeed Sally. While she is not a major A-Lister, the casting makes sense from a producer's perspective. Rankin is a phenomenal talent, and what's more, she is a perfect fir for this particular production's portrayal of Sally. And casting someone like her signals that the producers have an eye towards longevity: Rankin is wonderful, but not uber famous, meaning that the vast majority of tourists wont be buying tickets for her. They will be buying the Cabaret name, plus Eddie Redmayne. But Redmayne is not SO huge of a draw here that he cannot be recast with an affordable but fantastic talent down the road when Eddie's contract is up. Similarly, Sally can become a role for women to make their mark with and producers won't have to shell out big bucks to get a major celebrity (at least this will be their hope). The theater reno is going to cost an insane amount of money, so they likely cant afford to do expensive star casting if they want longevity and recoupment.