http://www.gamespot.com/articles/bioshock-creator-irrational-games-is-shutting-down/1100-6417821/
This just popped up on my screen. I never played the series, but I know a lot of people do.
Sounds like they are just moving on to a different scope of gaming and most the people are being let go so that a few are left behind to start something new. I wonder if someone else will pickup the title and continue it, or if it really the end.