https://www.vg247.com/2018/11/16/pokemon-lets-go-pikachu-eevee-pokemon-go-players/

I was just browsing around the internet when I stumbled upon this. It would appear as though GameFreak's humble plan to increase the size of the core Pokemon fanbase may just be working. Analysts have collected some data regarding Pokemon GO players and their stance on Pokemon Lets Go Pikachu and Eevee. The data was collected from over 55 million active Pokemon GO players.

15% plan to buy Pokemon Lets Go
(~8.25 million)

24% already own a Nintendo Switch
(~13.2 million)

13% of players who DO NOT own a Switch plan to buy Lets Go
(~5.4 million)

admittedly there are some things about this that sound a bit iffy, so take it with a grain of salt, but if this is to be believed, then Lets Go could be a system seller, and could to GameFreak's intentions bring in millions of new fans to the core series.