The Beta 4 version of Supreme Commander 2 0 1 3 Mod is available for users from the ModDB Download Section. A Changelog for Beta 4 that will be useful for returning players can be found on the same page. Players that are new to the Mod can check out the Cumulative Changelog to see the entire list of changes that has taken place in every up date so far.
To coincide with the new update, the mod team is holding a Tournament! It will be this coming weekend (on Sunday for most of the world). The tournament is labelled as 'all skill levels welcome', and is being used as a means to collect feedback on balance and playability, as well as to give the mod and game more exposure.
Interested in joining in on the tournament action? Please visit the SupCom2013 Challonge! Page for details and to sign-up.