Only three weeks after the introduction of the Overwatch Contenders, Blizzard have just published a news about a new league: Overwatch Open Division.

This new league is aimed at players who are ranked Masters and above in Season 4. Players can sign up as a team, or just get automatically assigned to a team if they don't have one.

The format or the prize remains unknown, but there was a note about the reward for playing all Open Division regular season games:
Players on teams who complete all their Open Division regular season games will receive $10.00 in Blizzard Balance, with more in store for those who make it to the playoffs.

Also, the league seems to be going for the long run with many seasons to come:
Each season in Competitive Play mode moving forward will provide a new chance to be eligible for the following Open Division season. And, in the future, top finishers in the Open Division may be able to earn opportunities to advance to Overwatch Contenders, the regional development league for aspiring Overwatch League professionals.

The sign-ups for the first season, which is set to start on July 3rd, are already open.

Last note about the regions and a possible connection to Contenders in the future:
Participating regions for Open Division's first season include Western Europe, Eastern Europe, North America, Latin American Spanish Speaking Countries, Brazil, Australia/New Zealand and Southeast Asia (support for additional regions is being planned for future seasons); each region has an online platform for building or joining a team.