I don't see it as a problem for Nintendo honestly.
when i first bought my Xbox 360 in 2008 it had a 20GB proprietary harddrive that would cost a fortune to replace with a bigger one, and trust i have wanted to on several occassions.
With the Wii U i can use any of the harddrives i had lying about that i was not using, currently i have my old 400GB harddrive connected to it but might change it for a 2TB soon, harddrives are very cheap when they are not proprietary.
If you you go and buy your console and know you want to be going Digital you should have the foresight to already own, or purchase a harddrive at the same time, and i personally don't know a single person younger than 35 who does not own one or multiple external harddrives, even non gamers.
