2K Games came out this afternoon and said that the rumors were false.
A few hours later, we now know that 2K isn't kidding.
Kotaku has broken the news that, in BioShock 2...
You play as a Big Daddy.In fact, you're the first of the lot, a so-called "renegade" Big Daddy who's on the hunt for a Little Sister of his own, according to a tipster who has the new Game Informer magazine in hand. You'll take out rival Daddies with your huge hand-drill and plasmid powers, claiming their wee sidekicks as your own. Similar to the first BioShock, you can choose to either harvest your Little Sister prize for ADAM or you can adopt her as your own.
That Little Sister comes in handy. She'll harvest ADAM from corpses strewn about Rapture, acting as a warning sign for when the Big Sister—the lithe, lightning fast enemy who will hunt your character throughout the game—has you in her sights. Based on her description, it sounds like she'll one hell of a fight.
From what we've heard, players will have access to all the things that made the Big Daddy such a menace in BioShock, with the character upgrades and options available in the first game expanded to keep things interesting. More details can be found in the new issue of Game Informer, which will be appearing in subscriber hands any second now.

Hurm... don't know what to think about this. I love BioShock, have become a huge fan of its thought-provoking lore. But the notion of playing as a Big Daddy... aren't those things intended to be big dumb brutes that are no longer fully human?
But as good as BioShock was, I'll trust Ken Levine and the crew at 2K to deliver the goods. Even if, at the moment, this looks to be a most bewildering role that they are set to land the players into :-)