It would help Nintendo out if they kept online play free as that could be a pro advantage compared to the other options. Their online is better compared to the Wii/DS/3DS (no friend codes and whatnot) but still needs alot of work to get up to the competition's features.
But...if it remains free all that shouldn't really matter.
Generation 8 Predictions so far.....(as of 9/2013)
Console that will sell most: Nintendo Wii U
Who will sell more consoles between Microsoft/SONY: SONY