It seems that Sony is future proofing by staking its claim for the next few generations of PlayStation consoles. It was recently revealed that the company filed trademarks for different terms. Those trademarks include terms for PS6, PS7, PS8, PS8, PS9, and PS10, which fits in with the naming of all previous consoles.
Piercesword (via Gematsu) discovered the trademarks, which apparently do not provide any details besides knowing what the names of potential consoles will be. Sony has done this in the past. In 2006, they trademarked the terms for both PS4 and PS5. (Although the original PlayStation wasn’t trademarked until 2000, six years after its release.)
As for the near future of the PlayStation brand, Sony is lining up for the release of the PlayStation 5, which is set to launch some time in 2020. The company states that it will be its most ambitious console to date. So far, it has been confirmed that the console will feature backwards compatibility and possibly a voice assistant to assist players in-game.
Although the video game industry is ever-changing, Sony seems content to continue naming their consoles in the same way for the next six generations. With the six to seven year lifespans of most products, we could potentially only see PlayStation 10 launch in 2050.