Given the fact that the Switch effectively has a 1:1 Sales Ratio with Breath of the Wild, it would be fair to assume that the switch has therefore sold at or around 2,837,078 by the 20th of May Since there isn't many people who have bought that system but not that game.

Oh you know there is. 
And it's probably well into its development cycle, Rockstar hasn't announced it and is not going to announce it yet because they see that GTA V is still selling like hotcakes x 2 and they don't want to cripple that momentum. They're going to hold off on announcing GTA VI until the last possible second, they're probably waiting for Sony and/or Microsoft to tease or let them know about the the PlayStation 5 and/or Xbox 4, hoping that they can repeat GTA V's success, note for note.

Big software week for ps4, beating the NS, XB1, pc and 3DS combined as the poster above just said.

Closing in on 400m retail. A huge milestone to achieve so early.

Nintendo shipped 2.74m by March 30th, and the Switch sold 280k just in the US in April, so I would have it at over 3 million by end of April.

I'm thinking you meant to quote me? Yes, it's most certainly coming. I'm posting my weekly GTA V sales comment, and to keep things obnoxiously repetative, with only a hint of freshness, I've switched over to sarcasm mode. As for the bolded: This is undoubtedly what Rockstar will be hoping to do. Late gen release, then hit us with an upgraded version. However, with things developing as they are in terms of hardware BC, it might not be possible for them to pull that off again. Sucks that we'll only get one true new GTA this gen though. amiright?

I guess that would also allow for 200k digital sales of the games in regions where the console was available but the game might not have been.

I don't mean to generalize or detract from what you're suggesting because you could very well be correct in that there is a % of people who do own a switch but for one reason or another decide they don't want to enjoy the definitive version of the game of the generation on a portable console which is was made for ... but I would really think you are in the vast vast minority. I know there was a point where the attach rate of Zelda BOTW was actually over 100% because people who couldn't even get the system were buying the game just waiting to get a switch to stick it in.... or to lick on youtube channels for hits...

MK8D is fantastic though isn't it ? :D

Oh yeah... it's a me, golden Mario!

Good sales for Farpoint. How come it never comes up in exclusive list wars?

Farpoint without US? Why?

Breath of the Wild has about 50% attach rate in Japan for instance. So there's a fair share of players not owning Zelda for the Switch