I think we're partially right. The Angels will take Rory first, back in time to New York. But it won't be just Rory's tombstone the Doctor finds - it's Rory's AND Amy's. And they both die the same day - the day Rory was sent back to. The Angels need
the time energies released by their demise to accomplish their larger plan for New York. And Amy won't consider abandoning the man who waited 2,000+ years for her to his fate alone, so it's off to 1930's New York we go...
That's gonna be the real drama/heartbreak of this episode. Amy and Rory's deaths are a fixed point in time. Though the Doctor and River will do their damnedest, by episode's end it will become crystal clear there is nothing...absolutely NOTHING...they can do to save them. To quote Tony Stark, "There is NO version of this where you come out on top."
Amy and Rory's final challenge, therefore, will be to sacrifice their lives in a way that denies the Angels what they want. And River's challenge will be to help the shattered Doctor pick up the pieces of his soul and move on without them - as well as her own.