Subject to change means anything and everything in the trailer could be changed. I don't know if you know what happened at bungie, but here is the gist of it: A few months before the original release date for destiny bungie put a supercut together showing the whole game in one film, basically a quick way for execs to get up to speed with how the game plays. The execs watched and didn't like how it played, so they extended the release date and cut huge elements of the story to work with how the game plays now, now that could have been a poor decision or a great one, we don't know. However that does not show that they cut content to sell it back, they would have had plenty of time to make dlc content over that year and probably already had some done.