Realtime Worlds, the Scotland based developer of All Points Bulletin. Even more intriguingly, this second MMO is actually the company's original MMO project!
According to Realtime's CEO, Dave Jones, during his keynote speech at GameHorizon, their original investment drive of 30 million dollars was actually for their new product, this unnamed MMO. However, due to the ambitious nature of the project, All Points Bulletin was moved forwards in the production list to give the company a solid foundation before moving onwards.
While all details of this next project remain a mystery, Jones has said that the company is very excited to move fowards with this next project, their original MMO project. While we can't first hand attest to how ambitious this project is, we believe that actually moving your project backwards just so you can get another MMO out first really says something about how ambitious the project is.