it is entirely possible to go back to cartridge based games.
1. they are faster to load and play than disc based game and will remove any loading screens or requirements to download to system memory.
2. they are more durable than discs.
3. a cartridge made with todays tech can hold more data than a Blu-ray
4. it is becoming cheaper and cheaper to make the cartridges as years pass while disc technology is becoming more expensive. (~$1 per dvd and ~$2 per blu ray)
that's what I can think of off the top of my head.
They are producing SD cards in sizes over 50GB easy. 64GB ones are fairly cheap right now.
Not a great example because they are slow and volatile, but the tech is there.