Nintendo just announced when the paid online service will launch and what it will cost.
Initially scheduled for Fall 2017, the paid online service will now launch in 2018. Until then you can play online for free after signing in with a Nintendo Account. The pricing for Online (in USA) has been revealed as well:
1 month for $3.99
3 months for $7.99
12 months for $19.99
This price doesn’t include tax and the rates for other regions will be announced closer to launch. The Virtual Console title as announced earlier will be done slightly differently. Initially thought to offer you a single title for a month, the service page mentions the following:
Subscribers will get to download a compilation of classic titles with added online play, such as Super Mario Bros. 3, Balloon Fight and Dr. Mario.
This implies a Netflix like service and Kotaku even got confirmation that you can play the games as long as your subscription is valid.
Nintendo Switch paid Online Service will launch in 2018.
Source: God is Geek