I agree with Soren. Nintendo is usually behind the times. You figure they would be the last company to go digital-only.
Whoever does go digital only is going to piss off retailers big time. Gamestop isn't going to make much off a console if the console itself is the only thing they can sell in store. Would those retailers even agree to sell the console in that case? They did sell the PSP Go but they sell other Playstation systems that do use physical media so Sony could always make selling the Go a requirement for doing business with them, which the retailers would take to not be denied PS3 and later PS4 sales. It's going to be something that will have to be dealt with. Someone like Nintendo, who is going to need all the help they can to sell NX's, is not in a position to have a major retailer like Gamestop or Best Buy not selling their console. It would look bad to not have your console in the same stores that used to sell your product. Anyone that could deal with that would have to have enough consumer demand that it wouldn't matter.