It's a weird choice...I mean, they've usually gone for the more violent/splatter-type movies, but Rosemary's Baby is an arty horror film.
That said, I'm not a fan of the original (I thought the ending was laughable), and I don't think it's a particularly sacred cow - I'm sure the new one will be fairly different if they want to get the young crowd interested. Much gorier, more violent, maybe a hot sex scene between Satan and whoever plays Rosemary.