And Sierra. It would be amazing if MS released the source code to some of Sierra classic Hi-Res/AGI/SCI games, or the engines themselves.

IIRC, Al Lowe had retained copies of source code from the early Sierra days, and was planning to release some of it publicly a few years ago, but Activision shut him down. Maybe MS would be willing to reconsider that now that they're pursuing historical preservation.

Space Quest IV!!!