According to Amazon’s listings, the PS4 copy is said to be temporarily out of stock, while the Xbox One version has been backordered. Now this is only Amazon which means that it is only one retailer. This means that you can go to the likes of Best Buy and GameStop to get your hands on the game, or any other local gaming retailer that you know who carries it.
However if anything it does go to show just how popular it is, and also echoes GameStop’s comments about the game exceeding their expectations with regards to its sales. That being said, it is possible for digital copies of the game to be sold out. Some of you guys might recall that in 2012, ArenaNet actually halted the sales of the digital version of Guild Wars 2 as there were too many players on the servers.
It resulted in a less than ideal experience for gamers, but thankfully Overwatch hasn’t gotten to that point yet.