It looks like it's going to happen. EW reported that a Bridget Jones 3 is in the works. Working Title Films has apparently been considering a third installment since 2009, and has finally decided to go ahead with the project. The London Evening Standard reported in March that author Helen Fielding had been working on the third novel and was in talks for a third movie. At the time she had said that she wasn't sure if the book and movie would be "the same thing." Well, they were barely the same thing for the second Bridget movie, so it seems that the third novel could easily be very different for the third movie.
It's not official, but Colin Firth revealed what the movie could be about in an interview last year. What did Firth say?