The road-map is a fairly complete list of features that includes not only the functionality already present in jBilling, but also when new functionality is expected to be released.
The upcoming new major release of jBilling, jBilling 3, will include a new GUI, done from the ground up and many new features aimed at making interacting with the system more easy friendly and product management available to business users.
The revised road-map includes jBilling 3 and other features that were released in recent versions as well. Major features like pre-paid balances and credit limits, were released earlier than expected, while others postponed. All the entries of the list have been revised. The road-map is located in this page: http://www.jbilling.com/product/road-map