Far Cry 1.5 headed to Xbox

Following up on last week's revelation that Far Cry Instincts might be headed for the Xbox 360 comes a similar revelation: day and date with the 360 release, the original Xbox will receive an updated version dubbed Far Cry 1.5 or, as a reader of GamersReports suggests, the Ubisoft Montreal produced Far Cry X. This comes via a Gamestop product list, a notoriously unreliable source of accurate information. Are these two games the same with some wrong tagging on Gamestop's site or two separate games extending the Far Cry franchise? If the latter, will it at least be backwards compatible?

[Thanks, alvin]