Eh, I'm not so worried about that.  The Wii U's issue was it's first 11 months had like one game of note that anyone cared about, that being Pikmin 3, and then finally there was Super Mario 3D World.  So it was a whole crap ton worse.  But the big crippler for the Wii U was the marketing.  The PS4 had an underwhelming start with exclusives, let's just tell it how it is, and 2014 had a lot of let downs in the multipat department.  But the "greatness is still waiting" jokes didn't stop anything because Sony played their PR cards right.  Nintendo needs to do the same, so we'll see.

And let's not forget that for Wii U owners the drought feels worse than it is since obviously most Wii U owners have Mario Kart 8.  But of course, the overwhelming majority of the more than 100 million dedicated hardware customers who could be drawn to the Switch never owned the Wii U and therefor Mario Kart 8 is a good offering.  Redout is another game coming to the Switch this Spring.  So I think there is enough to play in these few months, but they would benefit hugely from *physical* releases of all that are substantial enough for shelf appearances.

MK8 still isn't a new game though, anyone who really wanted it has had 3 years to buy it. So we could be looking at a nearly 3 month drought between Zelda and ARMS with only indies and old ports to tide over early adoptors. 

MK8 released on the Wii U. That's a problem by itself. Besides, it's been almost 3 years since MK8, which is the usual time between MK releases. Also, TLoU remastered sold pretty well, and many other remasters; this gen has showed that rereleases don't stop games from selling. And a big seller like MK won't stop that trend.

While MK8 isn't completely new, it does have new content, improved performance, and, most importantly, is now portable, so there's more reason to be interested in it for those that weren't before. Personally none of that does anything for me, only fixing the item system would of gotten me to buy it, but I've no doubt it'll still be a success like all Mario Karts.

Worth pointing out there is also Super Bomberman R, which I keep forgetting xD

It still isn't a new game though, just like God of War 3 Remastered wasn't a new PS4 game, and New Play Control Pikmin wasn't a new Wii game.

I didn't say it won't sell, but it's not new content, so early adoptors are still being asked to wait months between Zelda and ARMS with no substantial new games.

No one said it was a new game. I thought your point was that because it's not a new game people wont buy it, that's what we were responding to. So yes it's not a new game, but it is still a game from a top tier series, so it's inaccurate to say there's a drought between Zelda n Arms. Let's be honest, MK8D is gonna pull more people than Arms ever could, so if you're counting Arms you have to count Kart aswell.

I don't "have" to count anything. My statement was that there aren't any substantial new games between Zelda and ARMS, a gap of nearly 3 months, and that's true.

Sure you don't "have" to, but when talking about whether the system will maintain post launch momentum or not as you were, it's kinda silly to brush off such a huge factor in Mario Kart as not worth mentioning. Your statement implys that because Arms is a new game it plays a bigger role towards Switch keeping launch momentum than Mario Kart. Well we'll see if the majority agrees with that soon enough!