Cross-platform play is a huge deal at the moment, many developers are looking for a way to allow people to play with a bigger range of people from across the Xbox One, Playstation 4, and PC. This is such a huge thing that many are questioning whether Blizzard will work on making Overwatch cross-platform play compatible.
When asked Blizzard was quick to send out a response via Twitter, they have shared that at this time there is no cross-platform play for Overwatch, however they have not ruled out the possibility to introduce the function for the games console versions. The key word however is the console versions, Blizzard has confirmed they have no plans on console to PC cross-platform play, simply put it seems that cross-platform between the Playstation 4 and Xbox One are their only priority. The reason they won't look at cross-platform play between consoles and PC are simple, they have sighted balancing concerns that would arise from players using a keyboard and mouse verses those of us using controllers.
Personally I feel that this problem can be easily fixed, they should find a way to omit keyboard use and instead have players use a controller providing balance. I doubt this would happen but I think it would make sense