A recent post in the official Overwatch Twitter account appears to tease a new Sniper hero. This coincides with recent rumors that suggested a hero like this.
The account posted a picture of an in-game communications record from the character Mercy to Soldier: 76 and Reaper. The picture depicts a sniper rifle. Mercy appears worried about the “slippery slope to modifications that will inevitably result in a weaponized version of her technology”.
There have been rumors leaking online recently about a sniper character called Sombra. A character holding a sniper appeared in a Gamespot documentary. None of this is officially confirmed yet, but since Overwatch’s Competitive Mode finally released last week it’s likely that Blizzard will be adding new characters in the near future.