Has there ever been any confirmation that we will be able to access the streaming feature of the Xbox One, while the Xbox 360 is connected to the HDMI in port? It'd be really cool if that were the case. I'm not sure if the Xbox One treats the 360 gaming feed as a frame within its own Xbox One OS, or if you won't have access to the Xbox One dash at all when the 360 is turned on and connected to the hdmi in.
I hadn't heard anything about twitch streaming with anything from the HDMI in, but that seems like it wouldn't go over very well, due to enabling the streaming of potentially copyrighted sources (TV, movies, etc.). That being the case, I doubt that they would allow streaming of any external sources directly from the Xbox One.