Wow, so if there's any validity to the
reddit post, Gearbox basically gave priority to their other projects, Duke Nukem Forever and Borderlands 2, at the expense of working on Aliens: Colonial Marines. Gearbox would shelve A:CM to work on their other games and then overhaul what they had worked on of A:CM every time they went back to it. Gearbox outsourced whatever they had of the A:CM campaign done to Timegate so they could fully focus on Borderlands 2 and obviously didn't have enough oversight over what was happening. The campaign came back a disaster and Gearbox had no time left to fix it because Sega wouldn't provide them with any further extensions. And rightfully so it looks like. Gearbox can't lay the full blame on their sub-contractor. Not when Gearbox should have had full oversight and control over what Timegate was doing. Not when they set A:CM aside at every opportunity to work on other projects. Not when they themselves apparently had no vision of what the game would be and kept reworking what they had of the campaign done. This sounds like it's entirely Gearbox's fault, it's a mess of their own making.
Knowing A:CM was a stinker, Gearbox likely used the vertical slice they created to even get A:CM greenlit by Sega to peddle A:CM to the press and gamers. Knowing full well the vertical slice was no longer remotely indicative of what the final product was going to be. Classy. Right now Gearbox have got to hope that the review embargoes and Aliens brand carry the game through enough sales to break even before the bad word of mouth fully spreads.
Sega will likely never work with Gearbox again. Can't blame them.