It's Digitimes, they've got numerous things about the NX/Switch wrong, like they said last year the NX was launching last summer.
Personally I think the Switch will sell a healthy amount, but I'm not sure if it'll ever hit 20+ million in a year. The 3DS never even topped 14 million and basically 3DS has all the same franchise games the Switch is going to have minus Splatoon. Maybe they could inflate totals by having varying models, but after a while I think that card runs out of mileage too.
Nintendo would need a new break out franchise that's huge, like a *new* Mario or Pokemon or Wii Sports or Brain Training to get to 20+ million, you don't get those types of shipment numbers just from the same ol' franchise catalog + Monster Hunter + Dragon Quest + indie downloads that are available on every other system. You would need something new to drive hardware sales to another level.