I was looking on Halopedia's news report on this, and they had an interesting idea of what it could be: the official name for the previously codenamed "Halo: Chronicles".
That's what I heard. I'm feeling really conflicted here. Only Spartan III's have numbers over 150, but it also says Halo: Reach Falls 2010. That sounds like a referance to the novel, whic was just before Halo 1. Anyone with me here?
Actually, I've never seen the first freeze-frame... I can even see the outline of a city, or something similar to one... although I still really doubt that. I'm not going to jump to conclusions until the real location is revealed... this changes my opinion slightly.
Maybe that was an old Forerunner City-Planet? It's possible that, unknown by humanity, that much of their architectural positioning and cityscaping was modeled off of old Forerunner design? It would help explain the similarities of Reach and a planet so far off the galactic map that it had been previously undiscovered by all.
Although then again, if it was so far away from the Halos that it was "out of range", then that wouldn't explain why it seemed devoid of life...
A retcon is when some part of canon is redone or altered to make way for future canon. I find the "it's them" line most interesting though. I'm not saying this is post Halo 3 I'm kind of torn but I think I'm going to make a case for it.
People tend to not like the time travel theory but we know there were Forerunner artifacts on Reach, entire complexes in fact. So Chief could just be there at another place in time. I don't like this theory either but my goal is to impartially bring up anything of use. I think the opening line could also be a hint, "From the beginning you know the end." most people would say this is a dead ringer for prequel but we all know how Bungie is.