Meh, it sounds sort of like Xbox LIVE Gold to me, or something like paid online DLC. I find no reason to panic over this, Nintendo takes care of people who pay for their stuff, hell that Club Nintendo thing is pretty neat and got me some interesting stuff just for already having games from them.
If they do go to some sort of subscribed membership dealy, they will probably outline what you get with it, and without it to a point that makes the whole deal fair enough. TBH, if a subscription is required to play online, I can usually pass on this, because most of the up and coming Wii U games I want are single player-ish (I would like more serious couch co-op games to rise though). Most of my online play is done through PC, and it seems fair enough to at least consider the ways and means that other consoles use to attract players.
All in all, this hardly seems like its going to be 'required' for anything, so I am not worried.