I'll just get to the point: do you think the Constants and Variables speech also was a commentary on the state of game sequels and how they tend to ultimately have the same elements of prior entries into a said series? About the constants and variables: do you think there is more to this concept than within the game itself?
I may have thought to much about it, but it would make more sense this way. I can't see the people at Irrational Games using the scene at Rapture without thinking about how this game was very similar to the previous two entries into the Bioshock series. Whether it's the Vigors, the Handymen/Songbird, or the three constants Elizabeth spoke of at the end, these elements seem too specific of game design choices to not have some overlying message about something aside from the game itself.
I'm not trying to say the entire game was a commentary on the game industry; it may only be a quick nod to the overall nature of sequels in most entertainment media. But the more you think about the history of the development of this game, whether it be the choice of box art, the ad campaign before its release, or even the initial reveal of the game to the general public, you have to wonder if Irrational was trying to say something about how sequels (at least in terms of games) are handled as of late.