Speaking with Kotaku on the subject of future improvements to the xbox 360's backwards compatibility with the plain-Jane Xbox 1, Microsoft's Chris Satchell had this to say:
He said that Microsoft still has a team working on it, but that they won't continue to do so forever."At some point we're going to focus less on it," he said. "When you get to the end of this year there will be a reduced focus on backwards compatibility. There are so many 360 games out there. I don't know if it's important anymore."
While I'm sure we all have a favorite Xbox game that has yet to make it to the backwards-compatible list, it's probably time to give up hope. Stop living in the past, you curmudgeons! If you really, really want to play your old games, you can always dig the old system out of the closet.