This was a big concern of mine too. That's why as much of Jamcorder as possible is open standards.
There is also a local web interface, http://jamcorder.local, that is fully extensible by the user. And the BLE and Wifi APIs are not locked down. You can implement your own app.
The biggest limiting factor IMO, are Wifi and BLE still going to be in common use in 30 years? That's hard to predict. But the SD card will still be there. Its a tough problem.
I think that's about as good as you can do, short of putting a screen on it.
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There's even a feature identical UART interface for the device. Surely that will still work in 30 years.
Buy a standard midi to usb adapter (~$20), then do:
piano -> (usb) -> Jamcorder -> (midi out) -> adapter -> (usb) -> pc
It should give acceptable latency for real-time recording.