I hope that if and when Bungie will make a game also on non-MS platforms, it won't be a Halo clone, it would be unfair towards MS, it wouldn't really help its competitors and it would tarnish Bungie's image.
Halo, despite being a fruit of Bungie's talent, is also very closely tied to MS, just like Pokémon are to Ninty, both are part of specific gaming experiences and they wouldn't work as well on other platforms.
Sony has its gaming universe, it relies less than Ninty and MS on few very powerful 1st and 2nd party franchises, but it works well anyway.
All in all, each console maker does its best when it follows its way, not the others.