JMS made a very surprising and exciting announcement yesterday (see the entire thread for additional details):
The original Babylon 5 was groundbreaking in many ways - the serialized 5-year story arc, the special effects, and the complex web of events and genres woven together. Moreover, JMS developed rich, 3-dimensional characters, many of whom underwent profound transformations during the course of the series. For all of these reasons, I've been very resistant to the idea of a "reboot"; why try to "improve" or recreate something which is already so good. However, with JMS at the helm and the commitment of telling a different story with some of the same elements mixed in (not stepping into the same river twice), I am very excited to see this next chapter in the Babylon 5 universe. It is also noteworthy that Claudia Christian said that the surviving actors from the original series will be involved in the new show in some fashion.