In a forum post, Blizzard has officially announced that Season 2 of the Competitive Play in Overwatch is coming to an end fairly soon. They also said that, whilst the first season will end on the 17th of August at 5:00 PM PT, the second season is scheduled to launch on the 6th of September.
Blizzard has also stated that if you have completed your placement matches in Season 1, you are eligible for a neat spray and player icon, and will be available to you once the season ends. However, if you were one of the top 500 players (in both your platform and region), you will receive an extra player icon and animated spray, as well as the placement rewards.
If you'd like to find out more in the upcoming days, Overwatch's Twitter and Facebook will keep all of their followers updated.