Confirmed
Rihanna - we know that the new album will be called Anti and there will be a world tour to support the release
David Bowie - He has just released his lead single, the near 10 minute "Blackstar". What I do know about the album is it will be Blackstar and will feature only 7 songs, but they will all be very long. I do think this will be one for the serious/hard core fans.
Pixie Lott - She has been working on her follow-up to her self-titled album since January and performed a couple of her new songs at her recent gig at the Hard Rock Cafe in London. One of the new songs, called "Good Love" is really catchy and got a round of applause at the end. I really like her.
Possibility
Rita Ora
Lorde
Emile Sande
Alexandra Burke (I think as soon as she finishes The Bodyguard, it is into the studio to begin work on/finish off her delayed 3rd album)