According to Pablo Hidalgo the RO “ending never changed”;
http://www.starwarsnewsnet.com/2016/12/pablo-hidalgo-clarifies-bits-about-rogue-one-a-star-wars-story.htmlA bit odd, considering all the trailer shots suggesting a very different ending, but I’m guessing that he’s simply referring to the overall fates of the characters.
Act 3 =/= ending. I assume he means the last five minutes or so.