Someone mentioned the Wii U servers shutting down, so I did some quick Googling.
The Wii came out in 2006.
Mario Kart Wii and Brawl came out in 2008.
The Wii U came out in 2012.
The Nintendo Wi-Fi Connection was discontinued in May 2014, so you couldn't play online on the DS/Wii anymore. That's about 1.5 years after the Wii U came out. If you played MKWii/Brawl at release, you had 6 years with it.
SSB Wii U came out in 2014, Splatoon in 2015. Could Nintendo keep the Wii U servers online until say 2020, or shut them down 1.5 years after the Switch is out, at the end of 2018?