Steve is in an interesting spot, I suppose. Minecraft is the sole IP Microsoft own that they are willing to share on Nintendo systems. While many would clamor for Banjo and Kazooie, the blockhead seems to pulling all the right moves on Nintendo as they remain dormant. An adored, but lost in time franchise and character such as Banjo has little hope to compete against the massive moneymaking series cherished by millions of kids today, and one that will forever be held as an iconic gaming series until the end of time.
Steve is potentially an underdog as a top ballot contender. Sure, he's not asked much on websites with Nintendo fanatics and purists around, but globally he has incredible range. The argument that "people only like the game itself, not Steve" is moot when merchandise involving the character is in high demand and accessible to purchase. Clearly people like the character enough.
Would Nintendo and Microsoft be willing to negotiate? Possibly? Would it be easy? Well...there lies the problem. With Microsoft being a direct rival, it changes the ball game. Nintendo already have Minecraft on their console, so what else would they gain from Microsoft in return? They certainly won't get much support from them on their system unlike SEGA, Square, Capcom, Bandai, and Konami who are independent companies that develop games based on deals and fair trade. Is it possible Microsoft lend some of their other series to Nintendo? Not likely. If they did, they would have put Battletoads on the Switch to boost sales, as that's where most people played the series prior and where their market could be found for such a game.
Would Banjo be on the Switch? They didn't port Rare Replay despite their recent relationship, even though hat's where the majority of the franchise's fans are at.
The relationship between Nintendo and Microsoft is beneficial for big hitters like Minecraft. Microsoft get to put their game on another platform, whilst Nintendo gain some of that rich Minecraft pie as financial compensation. The people who want Minecraft on Switch already have a reason to get a Switch - the game itself. Steve in Smash would not change much. Would he break the Internet and add some hype? Yes. Would he increase sales? Maybe a bit, but I don't see sandbox genre fans going towards a fighting game in numbers. The people who play Minecraft on Switch are most likely Nintendo fans already, too. Why would the Xbox One or Steam player buy the console for one character?
So while he is popular, from a marketing standpoint I don't see how it works out for Nintendo's benefit at all. Smash will sell well regardless, and the hard work to obtain any sort of long-term benefit outside of Ultimate is near non-existent for them.
Chibi-Robo is a neat idea, and its possible that when the project was put into place he wasn't entirely out of the picture, but the little fellow seems to be going on a downward spiral. An appearance in Smash would be interesting, but I can't see him being a ballot contender or character Sakurai wants to add on love or potential.
Ninten x2
Ken x3