During a Q&A session with partner dev lead Frank Savage at Microsoft’s Build 2014 developer conference, the topic of Xbox 360 emulation came up, and apparently the folks at the Big M are looking into it.
Q. Are there any plans for an emulator for the 360 games?
A. There are. But we aren’t done thinking them through yet unfortunately. It turns out to be hard to emulate the PowerPC stuff on the x86 stuff. So there’s nothing to announce, but I’d love to see it myself too.
How important is backwards compatibility to you? It's worth noting that emulation support doesn't necessarily mean Xbox 360 discs will work on your Xbox One, but at the very least Microsoft could resell you digital versions of all those old games.