Blizzard have revealed more about Overwatch’s competitive mode including season length, skill-based ranking and rewards. We now know that each season will be two and a half months, with a two-week break in between. They’ll be based on real-world seasons based on the Northern hemisphere.
Game Director Jeff Kaplan also said that one of the main reasons for the delay was that roughly 35% of games were going to sudden death which they wanted to minimise.
The competitive ranking system will focus on a skill rating rather than a progressive rating. You can expect to gain and drop tiers as the season goes on.