"Overwatch"'s Competitive Play mode has been out for a few months now and has already gone through two seasons of ranked play. It still seems as though Blizzard is trying to figure out what works and doesn't work for the format, as the latest update for the game is changing up a few things for the mode once again as the third season started last week.
One of the biggest changes that Blizzard made in the latest update of "Overwatch" is a transition period between two seasons, called the Offseason. The Offseason comes about right after the current season ends and everyone's waiting for the next season to begin. In the Offseason mode, competitive play formats of the different game maps are still retained, but your rating will not be affected by wins and losses. Each Offseason will last only a week, which will be the only time for players to test team builds without fear of skill ratings going down.
Blizzard has also noted in a Battle.net forum post that they've made changes to how skill ratings are distributed in "Overwatch"'s competitive play mode. Designer Scott Mercer says that they're trying as much as possible to distribute players equally among skill levels in order to provide healthy chances of winning between both competing teams. If it happens that players get thrown into matchups where the odds of winning aren't close to 50-50 for both teams, then the game also adjusts the skill rating gains and losses according to the chances it calculates for you.
Season 3 of "Overwatch"'s competitive mode is now live for the PlayStation 4, Xbox One, and PC. After the debut of Sombra, there are no new rumors yet of any additional playable coming to the game. However, Blizzard has claimed that there were three designs ready to go, one of which was Sombra.