While a successor to the PS Vita might be the most obvious reason why Sony patented a cartridge design, the Nintendo Switch, which has proved incredibly popular, could be a big influence here.
The connection at the bottom of the cartridge looks as if it’s used to communicate with a console, and there’s also a circular hole that could be used to remove it or carry it around.
Back in May, Sony gaming division’s John (Tsuyoshi) Kodera said that "Rather than separating portable gaming from consoles, it's necessary to continue thinking of [portable gaming] as one method to deliver more gaming experiences."
While it’s important to remember that many patents never turn into actual products, evidence points to Sony’s cartridge being part of the company’s bigger plans. We’ll just have to wait and see whether that’s a PS Vita 2, a PlayStation 5 with some Switch-style functionality, or something else entirely.
We've also seen new PS5 rumors hit the web. Leaked photos of the PS5 were made public this week and the console is said to feature a Ryzen 8-core CPU, a custom GPU based on AMD’s upcoming Navi architecture, and cost $500. No mention of it using cartridges, though.