In the forum post, Overwatch Game Director Jeff Kaplan provided a very in-depth explanation of future plans that the team behind the game has. Right now, the main focus for Blizzard is the Competitive Play.
"Our big focus right now is Competitive Play. So Competitive Play is quite a big effort for us this time around -- almost as much work as the first version. We're playtesting it multiple times a day. We're also looking into/debating putting up a Public Test Realm for this feature.Even when it goes live, I anticipate our first few seasons will require iteration on the feature."
The Overwatch development team is also creating some new maps and heroes. POTG, replays, and spectator interface are also being worked on. Lastly, Brawls and Custom Games, as well as an update for progression, is on Blizzard's radar.
Please, visit the original forum post here to know more details on the developers plans.