Gotta love the gaming industry sometimes - it's like MS looked over at Activision, thought "Wow, they sure are making a shitload butchering their franchises", and then grabbed a shotgun and started yelling "Today is a good day for you to die!" at their greatest hits.
Not really sure where they can go with extending the narrative... I mean, didn't they as good as wrap it up at the end of 3, war over, flood dealt with for good, us squishly monkey type things able to get by on the parts of planet that Didn't get cyber-nuked?
(EDIT: I will also mention this - okay, so the characters in Warrior Within weren't much cop, but the gameplay was brilliant, IMO)