Given that we have multiple months of sales data now that show the Switch has great momentum and a nice tragectary under constrained supplies, I don't know why people here are attempting to refute an analysis firm's predictions based on prelaunch assumptions like the price is too high or there is not enough games. People are living in the past.
It has been said that the appeal of the Switch isn't just some vague hope that it sells like a handheld (in a market where people believe handhelds no longer sell), but that it captures the hearts of the diehard Nintendo fans that supported them through a lack luster Wii U and an initially underwhelming 3ds combined. Even without a more casual audience, overlapping consumers, and all the families that feel a Switch is too expensive (though I'd argue that kids getting their own individual Switch is less necessary than a 3DS since multiplayer is available on TV and on the go, which makes it a better deal for many families), just combining core handheld and console Nintendo fans should put them comfortably in range of the 3DS without having to "sell like a handheld", essentially because it's instead "selling like a Nintendo AAA handheld-and-console-development-teams-combined 1st party supported device with some of their biggest franchises already released in just the first 9 months".
I think this is analysts predicting that lapsed Nintendo fans (whether from the Wii days or further back) are interested in getting this as well as possibly other gamers who may be new to Nintendo. Just that the Switch is doing so well before even having it's first holiday shows great potential for the system.