Taken from their official investor relations website, as part of the company's fiscal report for the next financial quarter, Nintendo have released a document with the to-the-point title "Wii's Successor System".
It reveals the Wii 2 is indeed coming, with the system intended to be a replacement to the 86.01 million selling Wii. While no details about specifications, controllers, games, or the online system were announced, Nintendo did confirm that it plans to show more at E3: "We will show a playable model of the new system, and announce more specifications at the E3 Expo, which will be held June 7-9 2011."
On Saturday, we said we weren't going to get too excited about the rumoured October release date of the console, and it turns out we were right for doing so - in the document, Nintendo confirm the system will release in 2012, although which quarter remains to be seen. We wouldn't be too surprised to see Nintendo mirror the 3DS's release, with a mid-March date for Europe.
Either way, what's long been rumoured is now official. The Wii 2 is coming. Keep your ears to the ground, people.