Microsoft has stated that the 'Xbox One' will not be backwards compatiable, meaning it won't support previous Xbox 360 titles.
This is not a problem for those who plan to pickup the Xbox One this year but also the Playstation 4 which is based on a different chipset meaning they might not support Playstation 3 titles.
It seems Microsoft has no intention of making the new 'Xbox One' backwards compatiable to support games from the previous console. Some gamers are outraged at this and some have started petitions to try to get Microsoft to make the Xbox One backwards compatiable like this one on Change.org. 738 supporters are already supporting this initiative.
Microsoft has not commented yet on this petition. I'll keep you guys posted.