Sony has filed a patent for a game cartridge, for an as yet unknown device. The suggestion is that the cartridge could be meant for a handheld console. 

We don’t know what the handheld device might be, but there is a strong chance that the cartridge could be meant for a device to follow the PSP or PS Vita. This may perhaps be influenced by Nintendo’s recent sales successes with the handheld Nintendo Switch Lite (via LetsGoDigital).
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