Well online play for the wii is free, but will that change with the wii u?
Nintendo has no plans on focusing with online gaming communities, which belongs to the Xbox. They'll just make something basic. Ergo, they're not gonna charge you for something so meaningless.
They know how well pay and play was received...
If they didn't keep it free, it'd be a horrible business decision on their part. Sony could keep their next gen console's internet free and be the only one of said next gen consoles to have free multiplayer and the like. If I could have only one console, I'd be tempted to choose Sony over Ninty for that very reason, what with my wholesome lack of faith in Nintendo supplying a legitimate online service, none the less one worthy of being payed for.