A message from Ken Levine details reasons for pushing the game back a few months to add extra polish and make the game "into something even more extraordinary".
Originally slated to release this October, Bioshock infinite has now been pushed back until February 26, 2013. This isn't too big a surprise, the original Bioshock was released late too and given that I'll still be playing Borderlands 2 when this was originally scheduled to come out, I see this as good news. By all means, make a perfect game! Just don't get stuck in that Duke Nukem mode, LOL!
Here's part of what Ken Levine has to say (read the whole thing at the source link):
When we announced the release date of BioShock Infinite in March, we felt pretty good about the timing.
Since then, we’ve come to realize that some specific tweaks and improvements will make Infinite into something even more extraordinary. Therefore, to give our talented team the time they need, we’ve decided to move the game’s release to February 26, 2013. We wanted to let our loyal (and very patient!) fans know this as soon as possible.
I won’t kid you: BioShock Infinite is a very big game, and we’re doing things that no one has ever done in a first-person shooter. We had a similar experience with the original BioShock, which was delayed several months as our original ship date drew near. Why? Because the Big Daddies weren’t the Big Daddies you’ve since come to know and love. Because Andrew Ryan’s golf club didn’t have exactly the right swing. Because Rapture needed one more coat of grimy Art Deco.
Well, one less game I'll be seeing at 2K's booth at E3 this year.