HoTS recently underwent an overhaul, where their loot system changed and they introduced loot boxes as a way to distribute loot. In order to encourage people to play HoTS, Blizzard has again brought in the Nexus reward crossover with Overwatch. This time round they’ve offering an Officer D.Va skin along with sprays and loot boxes. Currently, the skin(s) are only available on the PC version however, Jeff has said that the skins (Genji Oni and Officer D.Va) will be introduced to loot boxes sometime in the future.
Because of this, we plan to add both the Oni Genji skin and the Officer D.Va skin to the normal, base Overwatch loot box at some point in the future (Source).
~ Jeff Kaplan
However, there is no set time on when this would happen. They’ve also staggered the release of the rewards over a 4 week period.
The D.Va skin is currently in game on the PC version at least, for you to look at if you’re wanting to have a look at it.
To unlock the rewards, you need to play Heroes of The Storm, with a friend, for 5 games per week. It’s currently unknown whether or not the rewards are staggered and you have to play a total of 20 games to get them all or weekly based and you play each week you’re after. It’s probably best to play 5 games each week, just to be on the safe side.