Based on what? At that price tag, I doubt it will be mass market, but perhaps I’m wrong.
I believe there is a large market of consumers in the US who can afford a $2000 premium phone compared to the $1300 iPhone Pro Max.
In China, reportedly JD.com's Apple store received more than 1.13 million registrations of interest for the Duo, at a starting price of ~$2400.
I could be wrong also, but I wouldn't be surprised if the iPhone Duo sells like hot cakes.
I could imagine that premium smartphone buyers, instead of upgrading their phones for minor camera and battery improvements, go for the device that unfolds into a tablet.