In 2007, RarePlay reported about the social features that would be included in email services. "E-mail providers like Yahoo, Google, Microsoft and others are now incorporating social networking functionality in their email offerings in mapping out the relationships between people and how are they related (social graph). An interesting experiment Yahoo (and similarly Google) is undertaking internally is called "Friend Finder". Friend Finder analyzes a user’s email traffic and indicates the friends with whom a user has strong email connections based on incoming/outgoing traffic and the frequency and speed in which two parties respond to each other." While Yahoo has already released an early version of the social application, Google has yet to make an announcement.
Some other messages from Gmail's code suggest that we'll be able to sort messages by priority and save messages in an outbox to be sent at a later time.
Gmail still have important features to be released before removing the "beta" tag: