Never had much issue with good DLC, let's just hope they know what's what. So far, it has been a mixed bag, I find the Amiibo concept appalling though, very costly and often a minimal amount of content. Their other DLC has been pretty good, especially compared to a lot of other publishers.

Bethesda's horse armor has yet to be topped by anyone!

DLC doesn't really consume much in the way of bandwidth since the bottlenecks are usually in the engineering field, and DLC is not nearly as engineering heavy as the core development phases of a game... assuming Nintendo develops similarly to Western and American studios.

Yeah I kind of realized this too, while reading the thread. Adding new levels, via DLC takes a lot less time than making entirely new Animations, 3D Models, Code, Textures, etc. for a whole new game. So like some other people said, it looks like Nintendo's DLC is just a matter of giving their art departments something to do while pre-production and coding for their next projects get far enough along to require art/sound/level-design assets. 

Nintendo's late to the DLC game and they're just trying to play catch-up lol

Well DLC is certainly something that Nintendo fans used to complain and also brag that all Nintendo games released finished, etc...
But I don't really think they have done more than standard in the industry. Also I very much doubt that even if they haven't done a single DLC they would have one extra game launched.

Uncharted Lost Legacy although having more than 6h of campaign was done by a very small team because they just did to have a story written, cutscenes made and "assemble" the assets to that story.

Game design, gameplay, engine, assets, all the heavy lift was already ready for they to use.

This is the same concept that allows day one DLC without having to cut out from the main game. Writters, animators, etc aren't being used on the last stages of the game so they are free to do DLC and optimize resources.

I'd say no because it doesn't have to be an either/or situation. Nintendo's a big company and they can keep steady releases while supporting prior ones. I think so, anyways.

They're also usually pretty good when it comes to providing bang-for-your-buck, like the examples of free DLC that others have mentioned. That can maximize both sales potential and player enjoyment of individual titles. If they stick to that idea I don't think there's a problem.