Today, the research firm issued its forecast for the Switch through 2020, which predicts that Nintendo will manage to shift 40 million units. DFC acknowledges that initial hardware allocations and a slim launch lineup will limit the system in the beginning but "demand is expected to be strong and the major issue will be whether the system can attract a broad audience starting in the holiday sales season of 2017."
DFC Intelligence head David Cole commented, "The Switch is a compelling piece of hardware that could potentially reach a much larger addressable market. However given the limited software and Nintendo's poor recent track record of introducing new products we have tempered our forecasts to be conservative."
DFC Report summary (broken link at the moment)
The market brief with an overview and forecasts is available here. But, there is a fee barrier.
GamesIndustry Article (James Brightman)
Switch me if old
EDIT:
The thread title has a mistake lifted by the gameindustry article. The 40M estimate refers to 'by the end of 2020', rather than 'by the start of 2020'. Therefore, sales for 3.83 years.