You wanted it. Psyonix wanted it, so here it is. It will be a 3v3 competition so be sure to sign up yourself and two of your friends. Registration starts on March 25.
The concept is clear:
Grab two friends and form a three-person team, then register starting March 25 to compete in the first season of the Rocket League Championship Series! Each RLCS season will span three months and feature teams from all over North America and Europe. The top-four teams in each region will be invited to compete at a live International Finals event for a shot at glory and their piece of the $75,000 prize pool! – RocketLeagueesports.com