Here are future intended features that have not yet been implemented or are implemented in an experimental way. As these are implemented, the text here will be subsumed by section's from the programmer's manual.
It's worth also referring to our roadmap, requested features list, and release plans.
Language extensions
Asynchronous Message-sends
Support in the syntax and run-time for asynchronous or "promise-returning" message-sends, as in the E project, is planned, along with other notions such as capability-based object-level security.
New Libraries
User Interface
See the in-progress design document for the user interface subsystem.