Looks like I may not be far off with the VR idea, this patent was uncovered today:
According to IGN: "appears to work similarly to Google and Samsung's smartphone VR solutions - the core Switch tablet is placed into a headset, which features lenses to create the 3D effect.
The patent also describes being able to use the detachable Joycon controllers while using the headset, although does not say whether they would utilise motion controls while doing so.
The patent description notes that in the "present embodiment" of the Switch, it will use acceleration and angular velocity sensors to perform head tracking. However, the patent also indicates that the Switch console may not contain those sensors, meaning the headset itself will perform the tracking. The patents were published today, December 15, but were filed on June 10, meaning the choice will almost certainly have been finialised in the interim."