I've always theorized that we might eventually go back to cartridges, but I think even when it comes down to it, losing a dollar vs losing 50 cents is a big difference over 5m sales.
EDIT: On top of which, I think the goal is to go as digital as possible and leave behind production costs associated with hardware.
I think a cool in between would be plug and play solid state drives that you could bring to gamestop, fill up with games and take around with you. That would eliminate the need for downloading, and eliminate production costs.
Like, imagine if you could take an amiibo or something, bring it to gamestop, copy a game onto it and bring it home. I think that would be pretty cool.