Game key cards will be around for exactly as long as the digital versions are, but in the meantime they are so much more flexible. Considering Nintendo still has the game servers for Wii online, we should be good for a while. It doesn't actually cost a whole lot of money, relatively speaking, to keep those servers up. Most of the time when these storefront shutdowns happen it's because of payment security issues. I suspect that, going forward, it will actually happen less and less since the stores will be programmed with that sort of thing in mind, rather than the explosive way they were originally created.

And hey, there's another cool thing about GKC. If the storefront ever goes down, you'll still be able to buy "used" GKC for quite some time after that. They really are the best compromise for consumers wanting something "physical," a publisher wanting to maximize profits, and a developer needing faster/more storage than a normal cartridge allows. Obviously I would rather have a physical cartridge, but I would MUCH rather have a GKC than a single-use code that ties a digital game to my account I can never get rid of and will have a hard time lending to someone.