As you said, if they were porting it to 360, a completely different (inferior) version will need to be made and would decrease sales of the Xbox One because Halo is a huge selling point for the Xbox game consoles. It has already been confirmed to be an Xbox One exclusive. Why are so many people hell-bent on getting an Xbox 360 port anyway? I don't remember people complaining that Halo 3 wasn't on the original Xbox...