Guys, we made one of the most critically acclaimed games of the past decade and people are willing to buy a sequel to it based on brand recognition alone.

It's quite possible it's named Bioshock because, well, it may actually be in the Bioshock timeline. With this new time rift plot point, its very possible this once seemingly isolated storyline could be intrinsically linked to the pretense of the first game, or possibly even a new direction for the future game.

Why not just call it what it really should be called?

System Shock 2 but in the sky at the turn of the century the sequel to System Shock 2 but underwater in the 50s.

Brraaaaand recognition.

Skyoshock.