Select PlayStation 4 owners who were part or registered as testers for the previous PS4 software beta programs
will have the opportunity to change their PSN Online ID as many times as they want. However, only the first ID change is free, after which the player is required to pay $9.99 USD/CAD and $4.99 USD/ CAD for PS Plus members as per Sony's announcement.
When you change your online ID, you will have the option to display your previous ID with your new ID, so your friends can recognize you. Once you decide to display your old ID or not, you won’t be able to adjust this after completing the online ID change process.
The preview of the mentioned feature will go live as part of PlayStation Preview Program which will run until the end of November. It was also noted that the feature will is only compatible with the PS4 games published after April 1, 2018, with the exception of some of the most played PS4 games launched before the mentioned date. The PSN Online ID change feature is scheduled to go live for the rest of the PlayStation Community in Q1 of 2019. Stay tuned for more gaming news and updates.
Source: PlayStation Blog