This means that your entire library of Xbox 360 titles will remain stuck on the former system. So definitely do NOT get rid of, or sell, your Xbox 360. Just like with the original Xbox before it, you will need to keep your old system if you want to play your entire library of of old games.
This news was expected, but everyone loves the ability to play their old games easily on the new system. So it’s still mighty disappointing. For the record, the PS4 also will not play PS3 games. Both systems have a new architecture that is too different from the former design.