We weren't specifically sure when the game would arrive on the Xbox Live Marketplace, especially since its original due date of December 2009 was moved to "early 2010", but a quick skim through the Classification Board's most recent classifications reveals the N64 revamp for Xbox 360,
Perfect Dark XBLA, has been given a big MA 15+ stamp here in Australia, leaving us to believe the game will be landing on the Marketplace very, very soon.
In case you've missed it, Rare's N64 classic and Goldeneye spiritual successor, Perfect Dark has been given the Xbox Live Arcade HD treatment and will be coming to a 360 near you in full 1080p HD glory with online multiplayer. It may not be Goldeneye, but it is most definitely the next best thing.
Perfect Dark was rated MA 15+ by The Board on 21st of December, 2009.