So, I've been thinking about this for a little while now. In regards to characters being chosen for the roster, and the timeframe in which they matter most (unless they're notably historic, iconic to the franchise, or are popular beyond their era), Smash has typically chosen from games only from a certain timeframe up until the project plan is finalized. For instance, Brawl borrowed Gamecube content, but Sm4sh borrowed Wii content despite the expectations being Wii U content.
We firmly believe that the project plan For Smash Switch was finalized in 2016. If this is true, then content from Switch titles up until now should not yet exist in the base game unless they made some sort of special exception to allow such things. Pokemon X & Y was an exception to such a case because it was in development at the same time as Smash, but Pokemon released a year sooner.
With such in mind, I say expect a lot of "Wii U" Era and "Pre-Switch 3DS" Era content to make up the new base game content. I do believe this would make certain Switch games untouched by Smash, such as ARMS or Xenoblade 2. It would also kill Super Bomberman R as a major title used to backup the requests for Bomberman. (Breath of the Wild is technically a late Wii U era game, and was delayed to allow for a Switch release, so its content will still make it into Smash.)
What this
does allow for is Xenoblade X, Pokemon Sun, Moon, Omega Ruby, & Alpha Sapphire, Donkey Kong Country: Tropical Freeze, Game & Wario, Yoshi's Woolly World, Yoshi's New Island, Kirby and the Rainbow Curse, Kirby: Planet Robobot, Star Fox Zero, Earthbound Beginnings (Virtual Console), Mysterious Murasame Castle (Virtual Console), Splatoon, Chibi-Robo!: Zip Lash, Code Name S.T.E.A.M., Devil's Third, Bravely Default. Bravely Second, Fatal Frame: Maiden of Black Water, Fossil Fighters: Frontier, Paper Mario: Color Splash, Mario & Luigi: Paper Jam, Metroid Prime: Federation Force, Rhythm Heaven: Megamix, and potentially both Yo-kai Watch 2 and Tokyo Mirage Sessions #FE.
If we want to be
really real, we should be
expecting content from these games in particular. These are all Wii U and 3DS games from 2014-2016. Yes, a small few of these games already received content in Sm4sh in the form of either trophies, stages, Mii costumes, or other forms of post-release DLC. And I do think that certain things from 2017 might carry into Smash, such as Metroid: Samus Returns for Samus' character design. However, that changes nothing in regards to
newcomers. Further beyond this, is that this whole game timeline excludes one major thing:
This is the game changer.
I've concluded that we should play it safe and not expect too much in regards to
Switch content. If DLC happens, and it
will happen, the Switch content will arrive in fashion. But I do not believe the base game will be where the Switch stuff will be.
That's just my analysis. You may take it or leave it, but at least receive it as a small warning of what your expectations may be based off of.