It's most likely never going to happen. Look at the length of time since Halo 3 was released, and it's still not on PC. They've made up their minds. If Halo: ODST drops and it's still not on PC by that time, it's not going to happen.
Proud Owner of:
250gig FFXIII SE Xbox 360, 250gig Xbox 360 S, black Wii, 120gig PS3 Slim, soon to be 3DS *___*