Xbox followed up its E3 press conference with a new episode of Inside Xbox with new details about Project Scarlett. Xbox boss Phil Spencer was on stage and revealed that the next-gen Project Scarlett will be backward compatible across every Xbox generation. Meaning you can play games dating back to the very first Xbox.
"We thought about our design for Project Scarlett we definitely wanted to make sure that we were compatible across all the generations. Not just with the games, but the accessories... For us it's really us respecting the purchases that our gamers have made on our platform."
This is the most comprehensive form of backward compatibility for any current- or next-gen console we've seen, but there are still some questions. Based on Spencer's wording, it sounds as though Xbox's current backwards compatibility program is moving forward onto Scarlett. So it probably won't be as easy as sliding a disc for your favorite Xbox game into your Project Scarlett console.
We also reached out to Microsoft to get a better understanding of Project Scarlett's accessory compatibility. While controllers for Xbox One and Xbox One X might work with Scarlett, it's unclear if devices like the Kinect, which the Xbox One X removed ports for, will carry forward as well.
In a statement to USG, an Xbox spokesperson responded, "Our focus is on reaching the broadest set of players with our games and empowering our partners to do the same. Nothing further to announce today. We'll have more to share on Project Scarlett in the future."
Either way, for fans with a library of old Xbox and Xbox 360 games, it sounds like Project Scarlett will continue to let you play those games. Though it remains to be seen if Microsoft has to first allow for backwards compatibility on specific titles in order for those games to work.