There will be a multiplayer beta for Call of Duty: Infinite Warfare and it will begin on October 14th. The beta will be available that day on PS4, before it is assumed to come to other platforms later.
This was announced today during the Call of Duty XP opening presentation. It sounds like you need to preorder to play the beta.
https://youtu.be/irIkbTen53k
There was a multiplayer beta for 2015’s Call of Duty: Black Ops III. It also started first on PS4 before later coming to Xbox One and PC. It seems like the same process will be applied to Infinite Warfare as well.
Activision did not say what will be featured in the beta, or even how long the beta will last.
The PS4 also gets exclusives for the game as well as being the first to host the multiplayer beta, 30 days of DLC exclusivity will also be there for PlayStation gamers to enjoy.