A collection of new orchestrations based on the original Halo title will be released on November 15th to coincide with the Anniversary Edition the same day.
The two-disc set will be released to "retail outlets worldwide" according the press release: however, a quick check of the likes of Amazon has the soundtrack's retail release as November 28th - so its seemingly digital only through the likes of iTunes next week.
Still, its got some competition: November 15th also marks the release of Deus Ex: Human Revolution's soundtrack album as well.