You didn't get Super Mario Advance for free, and that was a STRAIGHT PORT. Super Mario 64 DS was almost 1.5 version, and that also was non-pack in. Nintendogs+Cats? That's definitely a 1.5 sequel like what is being hinted for Mario kart and Splatoon and that was not packed-in.
I don't think Splatoon as a pack-in makes sense because it's an established IP, and it's not as accessible as a casual party game. Anything could happen, but Nintendo has followed a general rule when it comes to launch pack-ins.
Conversely we got Super Mario World as a pack in with the SNES.
Nintendo needs this hardware to sell. Having all their software in one place is useless if sales are slow. Going back to having a worthwhile pack in, rather than mini game stuff, is one way too do that. Especially since they're not willing to take a loss on hardware sales to drive adoption.
If Nintendo wants to try to chase casuals again with some mini game pack in, well, good luck with that. Core gamers and lapsed gamers will take a hard pass, and the casuals will stick with mobile.
Having an established IP as a pack in helps the launch price, whatever it ends up being, be more appetizing to core gamers sitting on the fence about Switch. That's who they need to be early adopting alongside the Nintendo diehards and fanboys if they want this to get off to a hot start and not struggle indefintely like Wii U or until a price drop like 3DS.
Else this just risks getting perceived as another overpriced, underpowered Nintendo console full of expensive games that rarely drop in price and is easily ignored by fence sitters who are only interested in a handful of their titles anyway and perceive most as too "kiddy/cartoony." They've got to shake it up this time and make it a more enticing product from pricing, pack in game, free online play, a more robust software lineup with more variety in genre and art style, a better VC etc. if they're going to turn things around.