A usb,WiFi,ethernet home raid that can be upgraded with a WiFi and ethernet module, the internal wiring and the usb raid module can be upgraded.
You could make a thin box which is glued onto the back of the Tele offering blue tooth, hdmi connected and usb powered. This could more neatly pack the pi experience with a module.
A key board system like the pi 400 but using a pi module means you would only have to upgrade the module.
A cd or dvd module and compute module in a powered box totally upgradable.
A totally modular laptop or as near as damn it.
Mini modules for modular portable devices.
Modular smart plugs.
A modular car 4G AI operated communicator and MP3/radio unit.
Mini module personal alarm clock.
Whether or not raspberry pi will build more on modules in the future who knows.